Updated 19th February , 18th April 1999; 16th September 2000; 7th October, 26th October 2001; 25th October 2002; 1st February, 14th May, 1st October 2006; 15th January; 12th February, 6th May, 28th October 2007; 24th January, 15th April 2008; 4th May, 24th August 2009; 16th January, 8th, 9th March, 24th June, 4th October 2010; 6th January, 12th May, 3rd, 11th October, 30th November; 9th December 2011; 13th January, 18th February 2012; 23rd April, 20th September 2012; 21st April 2013; 19th January 2014; 25th September, 17th October 2015; 14th October, 5th, 30th November 2016; 12th March 2018; 1st May, 1st July 2018; 27th January, 9th September 2019; 3rd November 2021; 8th February, 28th April, 9th June, 23rd September 2024

Incomplete description. It's almost certain that there will be some duplication of descriptions.

The most northerly entrance into the Four Valleys System (line survey). A route through into Cueva de la Hoyuca (107) exists - and ultimately to Cueva Llueva (114) and Cueva de Carcavuezo (81). The depth is taken to the downstream sump in Cueva Llueva. The resurgence (site 575) for water flowing west in the cave (rather than east into Cueva Hoyuca) was dived and connected through to downstream Cueva Riaño in July 2016. The cave was linked to Cueva-Cubío del Llanío in July 2019. A detailed survey of Cueva de Riaño can be found here. A list of the entrances into the Four Valleys System is found at the top of the Cueva Hoyuca description page.

Entrance Series

The strongly draughting entrance lies in a tree lined depression next to the track. The passage starts low - it often has to be dug out - and passes an earth run-in on the left. The entrance was dug out again during the Easter 2006 expedition, and a barricade built using an abandoned domestic oven and some rocks to attempt to stop mud being washed in again. After the short flat out section the going becomes easier with hands and knees crawling. After 50m a small inlet is met from the right and the way on follows this water and gradually increases in size. Several side passages are passed which are mostly oxbows but can cause confusion on the way out (follow the draft on the return if unsure which way to go). The streamway passes a small inlet on the left with gour pools, then continues as a mix of stooping and crawling for around 150m until it breaks out into an area with boulders and larger cross rifts up in the roof (unsurveyed). Continue following the passage at floor level to regain the stream and follow until some 250m from the entrance the stooping passage breaks out into a second larger area with holes in the roof. At this point it is possible to climb up directly back over the top of the passage you came along to gain a small dry sandy passage which leads to Double Barrel Passage via Grey Rock Chamber and is the best route to the upstream parts of the cave. Continuing straight ahead however leads within 20m to a 7m pitch reached via a slot down on the left. The pitch can be free climbed by traversing over the drop (after descending the slot) and climbing down on the far wall. Before the slot leading to the head of the pitch it is possible to clamber over a mud bank in the main passage to reach a larger ascending passage which eventually chokes. A few metres downstream from the base of the pitch the main stream is met and the passage size increases at Eureka Junction.
At the "first boulders in the entrance stream where you climb up" (about 130m in), an extension was dug into at Easter 2009, this has a good draught and a number of intersecting passages. Shown as "HSC" on the 0105.3d file.
Further surveying of new passage was carried out in the entrance series in February 2010, adding 349m. Lots of egg shells were seen in the extension. The first way up into it is near the entrance on the bend where you can first stand (stoop) along, just before the gour pool inlet is reached, only about 5 minutes in. There is a visual connection with the HSC series. The largest passages are a few metres wide, but all flat-out bedding planes. There is lots of calcite on the floors and blocking some passages below which certainly used to connect. (One passage from stuff nearest the entrance ends at a complete calcite blockage not far from the larger bedding plane passage). The end of the bedding plane passage nearest to Grey Boulder Chamber is too low, dig-able, but still a long way from Grey Boulder Chamber itself. The other end is heading towards Mad Axe Woman cave. A survey of the Entrance Series and passages off, can be seen here.

Downstream Riaño

Downstream the passage is 2m wide and 4m high and runs for 100m past some stalactites to a 1m cascade and a bend to the right, followed by more free climbable cascades of 2m and 3m. The last of these is the most awkward climb. The passage then turns left, and continues along a rift to a short section where you are forced to crawl in the water under some low hanging formations. This is followed by another bend to the right, leading to a pitch of 4m with a large pool at the base. At the head of this pitch an easy traverse gains a large dry phreatic tunnel which immediately turns left, with a smaller rift passage leading off right on the bend. (The large dry phreatic passage has been surveyed but no description has been found. I think the Ghost Rift series is somewhere in this area - Footleg. This was partially surveyed at Easter 2013 [and completed 1/8/2015? JSC]. Also surveyed was a steeply ascending oxbow with avens which emerges high in the roof of the streamway above the pitch at the Torno Inlet junction.) The smaller rift leads to an easy 4m free climb down to gain the floor of the active Torno Inlet. Downstream this inlet immediately flows under a low wet arch which can be bypassed via a short muddy moonmilk tube to emerge at the pool below the 4m pitch back in the main stream. The water from the inlet enters from under the wall here.

Downstream from the base of the 4m pitch the stream runs off to the left and the passage lowers to a crawl. This does not last long and after a further 200m of easy going, another pitch of 8m is met with an awkward crawl at the bottom. (At the foot of this pitch the survey data indicates a climb back up to the same level as the pitch head, and a continuation which rejoins the stream further down). The cave sumps 200m from this point and is then some 500m from its resurgence (575). Some higher level passages lead off from this lower downstream section on the line survey (see 'Grov Write up' section at the end of this description). In 2012, the resurgence was dived for 207m, continued at about -2m, and was finally joined to the main cave on 15th July 2016 by Jim Lister. See site 575 for details.

Torno Inlet

Following the inlet upstream the passage ascends a 1.5m step up followed by a couple of bends to a decorated corner where formations prevent progress at roof level, forcing you through a short wet grovel at stream level. The going becomes easier beyond as the stream is followed in a tall narrow rift until the passage develops into a wider phreatic section with the stream in a floor trench offset from the passage above.

Connection with Cueva-Cubío del Llanío With teams in Riaño and Llanío (3234), a connection between the two caves was dug out on 30th July 2019, mainly from the Riaño side. (Photos, video). The route through is along a sandy crawl to a squeeze into an aven where an excavated route through a calcited boulder choke enters Llanío in the Getting There Series. The connection was surveyed as part of batch 0105-19-01 and the connection line in the Survex file is
*EQUATE 0105_Riano.0105-19-01.5.7 3234_Llanio.3234-19-02.9
Over the same period, high level routes above Torno Inlet were also surveyed - this is the remainder of 0105-19-01. The combined caves can be seen in this Survex/Aven file

Back in the stream, a short section of wider gravel floored passage follows leading to a 90 degree bend to the right immediately followed by a 90 bend to the left. After these bends the passage develops into a tall narrow canyon providing relatively easy going for the next 125m to another prominent 'S' bend where the stream undercuts the right wall. (In October 2021, the Canny Passage was pushed down to a point above the streamway here. Looking up around this point should reveal a white marker.)
The undercut marks the start of the crabwalk, about 275m long (but feels much longer!). About half way along some helicites can be seen on the left wall, and a little further on a pinch at a calcite curtain has to be passed. A brief respite is met at an aven with a small active calcite flow down the left wall. An easy climb up to the roof here reveals the inlet to enter from an impenetrable hole, but the main passage at this level is a 3m diameter phreatic tunnel with the crabwalk trench in the floor. A side passage enters at this point, but quickly degenerates to a flat out descending mud slope where it becomes too low. Two flat out squeezes have been passed here, and roomier space can be seen beyond a third squeeze. The floor needs digging out to make these passable.

Back in the main passage it is possible to head back in the downstream direction at roof level via easy traversing on mud ledges, passing a second phreatic side passage on the right hand side (facing downstream). This has been followed to a junction where the left leads to a mud choke, and right leads to the base of an unclimbed 10m aven. Back in the main passage it is possible to continue the downstream traverse for a long way until the mud ledges become more precarious and sections of flat out crawling are required. It is a long way down to the stream here and a difficult down climb, so not recommended as an alternative to the crabwalk below. No further side passage have been found here.

Back at the bottom of the active calcite flow in the streamway the crabwalk continues upstream until the passage is blocked at stream level by some large slabs. The way on continues at roof level over these until the trench in the floor disappears and the passage becomes a wider stooping height bedding which soon lowers to a bedding crawl. This is followed until the roof rises and the passage becomes a narrow rift again at an area of formations. Shortly beyond this point the passage becomes a bedding crawl again and the stream emerges from a sump just beyond. Back at the area of formations a strong draught can be felt coming out of a narrow hole on the right at floor level (when facing upstream), with a wider passage seen beyond. This passage can be entered by climbing up to roof level and through a larger hole. An aven is reached after 4m which was climbed in December 2006 and made passable at the top. This is now rigged as a 10m pitch which is quite tight at the top (photo: Paul Dold) and breaks out into a 2m diameter phreatic passage above (the Road to Torno extensions).

At Easter 2013, a trip into Torno Inlet surveyed high level rifts, shown as "tornolinkpush" in the 3d file. One opinion of the pushing trip that carried out the survey: "Long trip that was abandoned by myself and 4 members of the 6 person team. It requires a much more considered approach and ... the cave is pushed by those with the necessary head for heights or that tackle is taken in to aid progress."

The Road to Torno

At the top of the aven at the end of Torno Inlet, a phreatic passage can be followed in two directions. One direction (due South) has a narrow stream trench in the floor, the other direction heads back over the top of the Torno Inlet passage (heading NW), crawling on a mud covered white crystal floor which is revealed when bits of mud stick to your knees and pull off the floor. After about 40m this breaks out into a larger phreatic passage at a T-junction. To the left the larger passage continues as a flat out crawl on flowstone. To the right the flowstone fills half the passage height apart from a trench along the right hand wall. To protect formations in the trench it is best to crawl along on the higher flowstone floor. Some fine curled up flakes of cracked mud are passed with care on a left hand bend, then the trench swaps sides a couple of times and has to be crossed over and back again to stay on the higher floor. A second T-junction is reached, where left leads via an unsurveyed oxbow to a window overlooking a chamber. Going right at the junction a squeeze past a flowstone bank is met. This looks deceptively larger than it actually is! After the squeeze you are forced to traverse over the trench in the floor, which contains delicate looking calcite slabs. The traverse ends at a 4m climb down alongside a fine thin calcite column (the Hypodermic Lance), to gain the floor of a chamber where the oxbow passage already described enters at a window 4m up the left hand wall. The far end of the chamber is reached by carefully crawling between two long straws. A flat out squeeze under the left wall leads to a parallel smaller chamber with more formations. The roof slopes down to the mud floor at the end of this chamber, at a point located at the same height and about 20m from the too low end of the roof passage above the aven with the calcite flow in the Torno Inlet streamway.

Back at the top of the aven near the end of the Torno Inlet, the passage heading due South leads quickly to a T junction. Right follows the stream trench along a much narrower passage which meanders for 25m to a second junction. The stream trench here comes from the right hand branch, and is about 3m deep but only 6 inches wide. Both passages beyond this point have not been pushed to a conclusion, but continue as sideways crawling around many bends.

Back in the main passage, going left at the junction leads to another T junction where it meets a tall rift passage. Right leads immediately to the bottom of a 15m high aven. The passage continues past the aven to a 2m climb up. Above the climb a bend left follows, leading to another T-junction. Right at this junction is unexplored. Left follows a tall rift, traversing part way up. A passage is passed on the right which leads to a ledge half way up to 15m aven below the 2m climb. The traverse along the rift continues past flowstone and curtains which have been cracked (presumably by seismic activity) until after 60m it is possible to climb down into an active streamway. The passage widens to 3-4m at roof level with many formations around this area. Upstream leads to a steep slope with large blocks. A large ammonite fossil is seen on the right here on a boulder. At the top of the slope the stream emerges from a boulder choke of large sandstone blocks. It is possible to climb up to the roof here and a possible bolt route was inspected on a trip at Easter 2011. Downstream in the rift a short section of fine sloping streamway leads to a waterfall which can also be reached from below via another route.
Another look at this Ammonite Choke area occurred on August 8th, 2019 (a "diversion" from the first Llanío - Riaño through trip), when routes were pushed along and up through the boulders. This was surveyed as batches 0105-19-02. There is a very strong draught in places and continuing bolt and free climbs give some hope that the bouldery area could eventually be connected with Torno.

Heading left at the junction just before the 15m aven, the passage passes under a large slab wedged in the rift to an easy climb down into a larger rift. This can be followed in both directions to reach the same chamber. Right passes fine mud drill holes in the floor. Alternatively left passes a short section of passage on the left which chokes, followed by a short crawl on mud. Both routes reunite in a chamber where the waterfall enters from above. It is possible to reach the top of the waterfall via an exposed traverse. At the far end of the chamber the water flows round a right hand bend along the floor of a section of passage with a fine phreatic tube containing stalactites and straws above a vadose trench. At the end the phreatic tube finishes at a circular hole where you drop down into a lower space with stalagmite columns all round (The Jail). The stream flows right and then back on itself to run parallel to the passage just followed. Squeezing through the bars of the jail leads to a flat out crawl on boulders to a sump. The stream flows into this sump in the direction of the upstream sump in Torno Inlet, which is located about 25m away on the same level.

Over 600m of extensions, including large, high level tunnel, were entered over Easter 2007. Full description and survey are to come.

Grey Boulder Chamber and The Mazeway

Climbing up into the dry sandy passage in the entrance series shortly before the pitch, the passage heads directly back over the entrance streamway for a short distance before a 90 degree bend to the left. The first maze like area is then entered, but most of the passages either form loops back onto each other or quickly choke, so it is easy to find the way through. A long straight section of passage is then followed past several cross rifts to a 90 degree bend left. After the bend the main route is generally straight ahead and then trending slightly left to emerge in Grey Boulder Chamber. This is in fact one end of a high rift with large boulders strewn around. The route through to Double Barrel Passage goes more or less in a direct straight line in the direction you are going when you entered the chamber. Zig zag left around boulders, then climb up about 1.5m onto the large grey boulder and continue in the direction you were going, leaving the chamber via a rift passage which leads to the complicated junction at the start of Double Barrel Passage after 20m.

Batch 24-09 (L=134m) was explored and surveyed in summer 2024 (drawing). Described from stream access, about 30m downstream of the Double Barrel passage inlet. A 3m climb up from the stream intercepts larger passage. To the right (East) a walking passage leads to a flat-out wriggle into an aven with passage seen above. Left, leads into the maze. Continuing straight leads to a steep slope and calcite and rock blockages at the end of the small chambers as well as a way back down into a parallel passage. This passage leads to a traverse over the stream and an alternative and harder way up/down to this series. At the end of the traverse is another inlet, that soon lowers to crawling height for approx. 30m. A crawl on the left is an oxbow above the stream. Straight on, the passage gains height until it becomes a tall rift which is almost blocked by calcite. A hole with sharp bits leads to a small chamber and a further squeeze that ends in a calcite choke. Back at the left-hand junction is the maze where despite all the junctions you are generally funnelled into a large, loose chamber "Not what we thought". There's a loose boulder slope at the far end with a connection to the calcite area described earlier. Below the chamber to the south is a short loose climb up to Batch 10 and a connection with the main through route, near Grey Boulder Chamber. [Alex Ritchie]
Batch 24-10 (L=23m). (Drawing) At the large cairn in Grey Boulder Chamber, below the North wall is a hidden crawl over boulders. This leads quickly into an enlargement in a calcite coated chamber. At the end is another crawl and a T-junction. Left has not been checked, right leads to a loose climb down then another up and finally another one down to reach Batch 9 below the Not What We Thought chamber. [Alex Ritchie]

Batch 24-11 (L=123m) was explored and surveyed in summer 2024 (drawing). Heading upstream from the main "green" route, this batch starts in the large streamway passage just beyond. It's a large inlet accessed via a steep slope/climb on the South side of the stream. A wide muddy phreatic passage leads to a junction, left is a blind chamber and right leads to a T-junction (Prince Junction) via a short sandy crawl. Right develops into a high rift, a passage off this to the north west leads to an 8m pitch down, with more passage seen to continue both across and to the left. Back in the rift is an awkward 6m climb down into a decorated chamber. The only way out leads into a short T-junction passage with the left-hand route blocked by mud and rocks. On the right is a hole hammered through calcite and then a drop short into the chamber seen below the 8m pitch. The only passage leading out soon gets too tight. Back at Prince Junction, the left hand passage leads into a large chamber "Albert Hall" with nice mud formations on the far side. This leads to a smaller chamber before a muddy crawl leads to an aven which is accessed via squeezing over a mud-bank. This aven has been measured to be 14m high. The only other way out is a muddy crawl that soon gets too tight. [Alex Ritchie]

At the end of March 2018, the Grey Rift extension, heading north from Grey Boulder Chamber was surveyed. (Batch greyriftnorthextn length 121m)

The large rift which starts at the grey boulder can be followed for about 100m past high avens (unclimbed) via a number of routes around boulders to a junction where a narrow rift heads left and leads into the Mazeway, a very complicated set of narrow dry muddy rifts which total some 500m in length. Through this maze an inlet streamway is reached. Upstream the passage increases in size and after 150m reaches a draughting choke which appears to be only 40m from the surface. This inlet passage was smoke tested in 1993 to Dormouse Cave (935) and another small sink east of that site. This is also the area through which Mad Axe Woman Cave (site 1630) might come in. The stream can also be followed downstream to the complicated junction at the start of Double Barrel Passage (described in the following section).

At the start of Dormouse Inlet, batches 24-12, 13, 14, 15 and 16 were explored in the summer 2024. The following descriptions are by Alex Ritchie.
   Batch 24-12 (L=81m) (drawing) is found by continuing upstream past the maze of passages to the "?" shown on the 2011 survey. Walking height passage leads after a crawl under a boulder to a junction. Right has only been partially explored but looks to close down, left continues along the rift. After stepping over a boulder a crawl is reached over a yellow-coloured pool "Puddle of P". The passage quickly becomes walking height again and a nice carrot like formation is passed in the roof - care! Another dubiously coloured puddle is passed under a rock bridge and enjoyable walking passage is followed past several junctions, that have not been fully explored / surveyed. After 30m one is forced to squeeze through a short rift at floor level before more enjoyable high and draughtting walking passage is encountered with many passages leading off in all directions. The passages on the left are just oxbows and have been sketched, to the right is batch 24-14 the Meaty Sticks Maze and straight on is the continuation of the inlet, batch 24-13.
   Batch 24-13 (L=271m) (drawing) The passage continues in fine style until a boulder pile is encountered that is easily negotiated by climbing over. After another 15m the fine walking passage appears to end. Straight on is a dead-end muddy crawl that ends in a too-tight, mud filled rift about 15m from Phil's Aven. To the left, before the muddy crawl, is batch 24-16. To the right under the wall is the first of many crawls under the right-hand wall. This leads into larger passage after a crawl under boulders. Larger passage is encountered punctuated with crawls. A passage on the right encountered, continues and is not fully explored where as the passages on the left all dead-end at mud walls as most inlets in this passage seem to do. What then follows is 50m of more alternating walking and crawling passage in a dry stream with numerous side passages (again blocked by mud walls after 10-20m, but not all have been fully checked). A large chamber/passage is reached, where a higher-level large oxbow avoids a crawl in the dry stream. This passes formations on the left and another oxbow behind a window in the formations. 20m further on the passage appears to end. However, this is false and to continue, one can either squeeze through at floor level or climb over the top and drop down via a 2.5m climb. After more narrower walking passage the start of the long crawl begins, this is 60m long although is punctuated in a few places one can stand up amongst formations. At the end is a small chamber with a cairn on entry. It's here batch 24-16 starts.
    Batch 24-14 (L=217m) (drawing) Known as the Meaty Stick Maze, this hard to describe series is located at the beginning of batch 24-13. Many passages - all tall walking passages - loop around in a small maze which covers an area 60m x 30m. Only the notable areas are described here. To the northwest is a chamber with a large boulder in it. There are several ways on here that have not been pushed, all at roof height, which could be climbed into without equipment. To the West is another boulder filled passage at a higher level. Dropping down between the boulders it's possible to continue as passage is seen and is accessible. However, this has not been pushed. To the south one seems to hit a series of high-level rifts, full of loose rocks, in places its possible to continue but I would not recommend it due to the general looseness. To the southeast is a high ramp with a very tall aven. Again, all continuing passages hit dangerous territory with false floors and loose rocks above, such as The Chamber of Death. These passages have not been pushed to the end because of this.
    Batch 24-15 (L=16m) (drawing) Not far into Batch 13 at station B6 (where the muddy crawl way dead-ends) is this short passage. Starting off large, this heads west and soon becomes a narrow rift after a mud-slope. A squeeze through slop leads to continuing passage turning south which gets too tight at a drippy inlet/aven.
    Batch 24-16 (L=92m) (drawing) Accessed by going to the end of Batch 13, the passage continues as a crawl after a small chamber. Straight on is too low, so instead one turns right and follows a slope up over calcite and then through stal grill before entering larger passage. A steep slope down leads into a well decorated wide and high passage and after 20m a well decorated large chamber is reached, which contains some long straws. The way on is up the calcite slope to the southeast which briefly lowers to a crawl with tree roots before again opening up into walking passage. Unfortunately, all passages from here close down, and are either blocked by mud or are too tight. There is a strong draught in the crawl that reaches this, but it's then lost. There are lots of tree roots to the south and west as well as an abundance of flying insects indicating this passage is close to the surface. The western most passage has a 4m high mud and root filled aven that must also be very close to the surface.

Batch 24-08 (L=40m) was explored and surveyed in summer 2024 and heads west before Grey Boulder Chamber is reached. A narrow crawl leads to a short, loose climb up into a larger rift passage. Left closes down quickly to a too small tube that we presume connects to the main passage further along. Right shrinks to a flat-out crawl after 15m, this continues this way with only a slight enlargement until the end, where it is choked. [Alex Ritchie]

Upstream Riaño

   Upstream from Eureka Junction, the passage has some deep pools until a step up is possible and the stream flows across a sandstone floor. An inlet - Pessimistic Passage - enters from the east at the first right-hand bend with a large pool, and was first properly explored and documented at Easter 2024 as batches 24-01 to 24-05, then as batches 24-17 and 24-18 in the summer.
    (0105-24-01) The far side of the pool, leads to an easy sandy crawl that drops you into the stream. After about 15m the passage grows in size and you can stand. At this point another stream comes in from a passage choked in cobbles. Continue upstream for a short while where a spiral climb takes you out of the stream into the roof. If the climb is missed then a flakey stream passage leads to an easy squeeze on the left into the same passage.
    At this point to the left and behind is a short upward sloping muddy passage (0105-24-02) that terminates too tight. The aven above appears to be a phreatic solution pocket.
    Back in the main stream (0105-24-01) the passage continues as a wide and tall rift, where one traverses over some boulders to come back down again at another junction. To the left here is a steep slope up leading into a high chamber with another steep slope / climb leading to another chamber with twin avens that are unclimbed.
    Back at the junction, taking the right-hand option, one is taken back down to the stream, where the passage degenerates into crawling/sideways shuffling mainly at stream level for about 60m. Here there is an important inlet on the right, described lower down. Continuing along the stream, the passage degenerates further requiring several sideways crawls past protrusions in the water in places, before relief is gained in a standing height "chamber". An inlet enters from above as a small waterfall the passage, however is too tight.
    (0105-24-04) The main passage continues past the waterfall as a crawling passage, before the roof lowers forcing a flat-out crawl in water which eventually sumps.
    Back at the important junction is the way into Pessimist Rift (0105-24-03). To the left of the rift is a short, decorated passage that leads back to the stream with an aven (unclimbed). The rift is mainly sideways going with some crawling on ledges / floor for 20m with lots of sharp protrusions (that we may hammer off). Thankfully, by heading upwards 5m further after a too tight rift on the left, relief is gained where the passage widens. (The too-tight rift likely goes back to the stream, as the water can be heard).
    The passage is now a series of chambers with some decorations connected by a much wider though slippery rift. After 50m this passage drops to a dug, flat out crawl, "Fin". In a tiny chamber beyond there's a squeeze down a sandy slope, before immediately a third squeeze leads back up into a large chamber which crapped out. This is the largest so far: 10 x 4 x 3m). This interesting chamber is festooned by formations on the right, has an active stream and has two exits (an upstream one and a downstream one). Upstream the passage is small and is currently blocked by a rock protrusion 6m in which could be removed. Downstream is a large high-level passage 3-4m above the stream, that progressively gets harder and has many levels between flakes. The downstream water disappears under the wall and the rest of the passage is upstream. Following this, the middle level seems to be best on the flat-out bedding above the rift. (0105-24-01) After 20m of reasonably hard going a hole above of 2m leads to larger passage. This comfortable passage goes on for 60m and is mainly walking along the rift with formations. The rift degenerates here, and a climb up of 4.5m is followed immediately with a slope down drops into the continuation. Unfortunately, this soon closes down due to calcite.
    A tight hole before going uphill leads down into muddy, hard going passage near stream level. The Easter survey ended here, but the passage continues in tight squalidness for at least 50m, and carries on, though it's horrible and hard-going. [Pessimistic Passage description by Alex Ritchie]
    Batch 24-17 (Length=115m) (drawing) From the logbook: Surveying conditions were challenging; sticky mud soon coated everything. We carried on for 120m until the disto ran out of battery. At this point there was a good echo and the sound of falling water ahead, so we dropped down the rift and carried on another 20m to enter a 20m x 6m x 15m chamber (The Redeeming Feature). Two inlets entered, one straight ahead which looked small but passable, and a more interesting looking phreatic tube in the right hand wall. Both needed a c. 6m free climb, but would need a rope installed for the return. The route continues as batch 24-18.
   Batch 24-18 (Length=70m) (drawing) From the logbook: The route to the phreatic tube was free-climbed a ladder attached. At the top, a chamber has another climb up, rigged with a handline. Up the handline, a short crawl leads into a chamber with an easy climb up into an ascending rift into another chamber. A short climb up in this chamber leads to a too-tight continuation. A hammered squeeze (video by Tiff Cooksley) enters a final chamber, which has a possible continuation up a climb that would need bolting. (Video by Tiff Cooksley).In total, we surveyed 70m. As well as the possible bolt climb in the final chamber, there is a waterfall flowing into the far end of Redeeming Feature. There seems to be caveable passage above - about 6m up. This would probably need bolting.

Back in the main stream, upstream of Pessimist Inlet, the route can be followed round several dog legs and becomes narrow before reaching a complicated joining of ways with a prominent stalagmite on a boulder across the stream. Just before this junction an inlet enters from the left carrying the main water from upstream Riaño. However a larger dry passage enters at the complicated junction just beyond, providing an easier route to the upstream part of the cave. These parallel wet and dry passages make up Double Barrel Passage. To the right (opposite the dry part of Double Barrel Passage) an ascending 2m wide rift heads back to Grey Boulder Chamber and the entrance series. Straight ahead is a quite large inlet and this can be followed into The Mazeway.

Back at the complicated junction the main stream can be followed up the low and wet passage, but the larger dry part of Double Barrel Passage is the preferred route. This passage continues in a straight fashion for about 150m past a stal grill until the stream is rejoined. The two passages continue for another 50m in the same general direction with progress made variously in the wet or dry passage until an inlet is met on the left near the first of two large swirl domes. This inlet (Energetic Between the Legs) was pushed at Easter 2006 and in August 2006 to add 370m of new passage to the survey.

Beyond the swirl domes the passage becomes larger at a sharp left bend with large blocks on the floor. Just past this point a walking passage on the right leads into a series of "coffin level" type passage which becomes too tight after 120m. Along the way two draughting avens are found. This area is not completely explored. Continuing along the main large sandy floored passage, a second passage leads off on the right into the same series of passages as the previous side passage. The main passage continues to another junction where the route branches. The left branch leads to Cat Print Passage, becoming a hands and knees crawl after passing an area of broken calcite. "Cat" prints are visible in the mud at this point. After 40m the passage ends in a muddy chamber and a 2m awkward climb leads to the base of an 8m high aven. This can be free climbed up a narrow slot and is the original way into the Upper Series. At the top of the pitch a number of small passages lead off and all appear to rejoin the main passage further to the southwest.

The right branch from the junction at the start of Cat Print Passage passes under an aven with a loop of rope hanging down to enable a ladder to be pulled up. At the top of this a meandering passage leads to the Upper Series. An easier route to the Upper Series is found by passing under the aven to another chamber with boulders on the floor. Here a streambed flows from left to right across the chamber. Downstream leads back into the "coffin level" series of passages. Upstream continues for around 150m until the survey ends(?). Across the chamber to the right a passage leads to a cross rift. At this point a sandy slope leads up to the left, and is the start of the Upper Level Link route to the Upper Series. At the top of the slope it is possible to climb up 4m in a narrow rift to gain a chamber formed in a bedding. From the top of the climb, go across the chamber to the left to a point where you can climb down a rift to a floor which slopes back up to the height you started at (on the reverse you need to traverse across from the top of the slope to regain the top of the climb down). Just beyond this the passage emerges into the large phreatic passages of the Upper Series.

Batch 24-07 (L=36m) lies east of Pendant Chamber and in the vicinity of Up to Glory. The description (Dave Barrett) is edited from the summer 2024 logbook. Loose ends in Riano central intermediate passages as shown on this survey. Blue lines are surveyed and the blue circle shows the checked area. Total about 30m of crawling passages on dry mud floor. One end connected with another. Other two passages ended in too tight or mud to the roof.

Energetic Between the Legs Inlet

Starting as a tight awkward rift passage requiring some flat out traversing, Energetic Between the Legs enlarges to a trenched meandering stream passage which is high in places. About half way along this length the passage changes to a long straight narrow rift until eventually it breaks out into a larger area above at an aven. The top of the aven can be easily reached by climbing up in the rift a few metres before the aven is reached, to gain the floor of a chamber of hanging death roof pendants which resemble large teeth (the Molars of Doom). This area contains much broken and unstable looking rock hanging from the walls and ceiling (care!). The stream continues beyond the aven in a too tight slot in the floor.

The top of the aven is in the corner of the Molars of Doom chamber with a sandy slope leading up to more stable ground. A dry meandering inlet passage also enters at this point from the left wall (when looking up the slope) at the top of the aven, and has been pushed for around 50m until the going became too arduous (unsurveyed). Up the sandy slope a crawl under a large boulder gains a further ascent to the top of the chamber where the passage narrows again. Up to the left a steep climb up loose sediment has not been attempted. To the right a step across onto a sediment floor quickly chokes where some helictites can be seen. Continuing into the narrowing passage a hole up on the right leads into a small chamber where another hole at the foot of a boulder slope gains a low wide passage with dark roof pendants which come down to the floor and sparkle with crystals. This passage leads into a large chamber (24m x 4m x 5m). Up to the right from the sparkling pendants leads to a climb up into passages above the chamber. Described from where you first enter the large chamber, to the left leads to the end of the chamber where the way on is choked with sediment. This passes under a rift in the roof which is blind. Straight on across the chamber leads into a winding crawl which ends at a double constriction with a draught, and space visible beyond, but too tight to pass. At the right end of the chamber a passage seen at the top of a climb up the opposite wall soon chokes. Turning right at this end of the chamber a climb up leads into a phreatic roofed continuation of the passage. A second climb up leads to a junction. Left at the junction leads to sediment choke. Right leads past a fine swirl dome to a dead end. An ascending calcite floored phreatic tube leads up above the climb and ends at a calcite blockage. Below the climb is the alternative route down back into the passage with the sparkling pendants.

Part way up the sandy slope in the Molars of Doom chamber it is possible to climb up to the roof and traverse back over the aven (exposed!) to gain a phreatic roof tunnel with a flat out crawl over a false floor. A pretty section of passage follows where you leave deep footprints in the sandy floor, past some formations until is closes down to a body sized tube. This emerges 3m up the wall of a large chamber with a 5m deep pit in the floor at the bottom of a conical funnel of loose rocks and sand. The near edge of the pit is a thin suspended false floor of loose fill. A tantalising slope leads off at the bottom and the pit has not been descended. Past the pit the passage continues a short way before closing down abruptly at a 180 degree bend. There is also a possible way on at roof level opposite the point where you enter the chamber. A crawl space can be seen to continue for up to 20m before going out of sight, but attempts to scale the 4m loose sediment wall to access this passage were unsuccessful due to lack of any suitable equipment.

Upper Series (still to be edited)

The main passage in this direction is an impressive phreatic tube varying between 5 and 10m high and wide. A passage on the right becomes too small at a choke though there is an alternative way back to the main passage by traversing round The Pit, a large hole which has not been descended.

Continuing in the main passage through a flat roofed area the passage gains height and width. After an awkward climb over boulders another passage is met coming in from the right. This is very well decorated and splits after 50m at the base of a 3m climb. The right branch is choked by stal after 120m but the left branch although smaller has not been explored to an end.

Back in the main passage the lofty gallery continues for some 100m until an inlet is met from the right. The passage now closes down to a miserable flat out crawl in the stream with a calcited choke above. The strongly draughting crawl has been connected to the Second River Inlet in Cueva de la Hoyuca (107). The inlet on the Riaño side of the connection has been followed to a high rift passage which after 200m finishes in a high aven and a choked chamber at a lower level. An search in this area for a "pitch 8m" failed in the summer 2010.

In the summer 2012, one trip surveyed passage due south of Pete's Way in the Upper Series adding 91m to the length.

Batch 24-06 (L=72m) was explored in the Upper Series in the 2024 summer expedition. The description (Dave Barrett) is edited from the logbook. (See Riaño 2011 survey)
   A small passage to the north off the fracture area after La Playa. Crawl through the breakdown and the passage proper starts at station 3 just before a slide over a rock. The passage is about 2 metres high, phreatic in origin with roof pendants and gloppy mud on small ledges. There is a vadose channel in the floor. Ahead it stops in a mud blockage. Left at the junction goes to smaller route until it meets a flat out crawl to a hole in the floor. There is a slight draught.
    At station 3 is a water worn rift going up which was climbed to about 8m and it continues. Rift is in the same rock and style as around the entry point into the Upper Series. At the bottom at station 3 is a mud blocked passage.. A few metres to the west in the fracture zone is another rift up, not climbed. It is marked on the drawing. The fracture area has a crack in the roof edge and side on the east side which is in line with the choke at the end of La Playa. The choke and indeed all of this area has very fresh air. Some drippy water only. Fracture orientation broadly NE-SW. The fracture area is not marked on the current drawn survey. (24-06 drawing)
   Amendments were also made to the survey in this area (amended survey)

Grov write up

In 1991 the downstream passage was pushed to major extensions which needs writing up by Paul Stacey etc. In this area, near the end of the downstream passage some 46m was surveyed in 1992. The inlet passage splits into 2 smaller inlets about 30m from the main passage. Both go to major choked areas. The right hand inlet has been followed into the choke for about 30m.

About 15m further downstream on the left is a steep boulder slope to a climb up boulders into a chamber on a fault with two avens in the roof. The inlet passage across the chamber has been followed along walking passage to a low crawl and choke. None of this 91-92 extension is on the graph survey.

At Easter 1993, a pitch was descended on the right hand side of the main passage, some way from the Anastomosis climb.

L. Mills located individuals of Cantabroniscus in 1985.

Over 3 days in December 2007, the 89cents Tinto Extension (248m) was made. This sets off in a series of climbs and traverses heading southwest from the vacinity of Cat Paw Print Passage, apparently ending 3m below the surface some 70m from the nearest site in the "Hoyuca-Riaño corner".
This was re-examined at Easter 2008 along with the Acid Bath and Pray Aven - descriptions to come. The Easter 08 trips added 154.7m to the length.
Over Easter 2009, bolting up Daddy Aven (off 89 Cents Tinto passage), started in 2007, was completed. The first level was reached at about 10m (with no passage) and continues in a scramble / free-climb with a ladder to reach another 15m in height to a calcited slot with a choked, body-sized chamber. Some new exploration also occurred down a flat-out crawl heading away from Acid Bath Chamber. A passage to the left of the aven was pursued to a steep slope where a chamber with stals can be seen through a tight squeeze.

In the summer 2011, the area off the Acid Bath (heading towards Hoyuca) was looked at and the write up appears here. The was also a trip to the most southern passage where a pitch was descended. The writeup appears here.

   Over Easter 2018, the Matienzo Karst Entomology Project (led by Tom Thompson) followed up a previous study by collecting bugs, spot sampling and setting pitfall traps in a number of sites under a Cantabria-wide permit. The Entomology Project carried out some work in this cave without collecting or sampling.

The cave appears on the Cueva Hoyuca and the Four Valleys System Hydrology diagram.

Link to entry in the Cave Diving Sump Index.

The speleo club Viana (from Guadalajara) have published a number of documents (descriptions & surveys, including gpx, pdf and jpg files) relating to the system. See their Cantabria page and the Zona de Matienzo section. [This appears to be open only to registered members with new members not allowed!]

Detailed Surveys : Original 1974 survey

21st Century resurvey

2008 24th Jan	Hoyuca entrance & Riaño	B&W png file
2008 24th Jan	Hoyuca entrance & Riaño	colour png file
2009	Upper level 1	B&W png file
2009	Upper level 2	B&W png file
2009	Whole cave with part Hoyuca	colour png file
2010	Entrance Series & HSC	colour png file
2010	Riaño + Hoyuca ent. series	colour png file
2011	Riaño	colour pdf file
2011	Riaño + Hoyuca ent. series	colour pdf file + notes
2024	Riaño plan	pdf file Tunnel import

On Paul Fretwell's latest version of the Fours Valleys survey

Line Survey : 4 Valleys System line survey (2010)
On area survey :
Survex file : Riaño only (now) :  4 Valleys System & surrounding caves (now) : 4 Valleys - lite (now) (Coordinates altered to fit ETRS89 datum, April 2014.) : just 0105 + 3234 (joined 30th July 2019)
Passage direction rose diagram: Four Valleys System
Hydrology (Terry Whitaker): Hoyuca and the 4 Valleys System