Updated 19th February 1999; 4th June 2002; 15th April 2008; 5th October 2010; 18th January 2011

This site is marked by a tree on the western side of the line of depressions. This is the deepest straight drop in the area, deeper than Sima del Cueto (041). Marked 212 and, on a rock face at the top of the pitch, M-49 in large green letters.
The green marks were painted by the Sociedad Espeleológica Alto Duero who explored the site later than the 1980 descent, naming it Sima M-49. A 7m climb up at the base leads to a choked p26m. Confusion with positions resulted in site 1785 being created. There is only one 164m pitch - here at site 212.

References: pers comm., 1980; Corrin J et al, 1981b; Corrin J S and Smith P, 1981; anon., 1996b (logbook); García José León, 1997; SEAD website; anon., 2008c (Easter logbook); anon., 2010c (summer logbook); León García José, 2010 (Volume 1 and Volume 2) (survey)
Entrance pictures : yes  and on the SEAD website
Underground picture(s):
Detailed Survey :  On the SEAD website : elevation from León García José, 2010 (Volume 1 and Volume 2). (Cantabria Subterránea. Catálogo Grandes Cavidades.)
Line Survey :
On area survey :
Survex file :