4005: Francés, Sima del
Riolastras 30T 455586 4802297 (Datum: ETRS89. Accuracy code: U) Altitude 217m
Length 13m Depth 13m
Area position

This site has been explored and surveyed by the Grupo Espeleológico de Santander del C.A. Tajahierro. Their survey is published in Exploraciones en Solorzano (Santander) in Los Sótanos de la Tierra, No. 5, 1980, Santander (ref. 1980a). Unfortunately the entrance position (along with many others in the publication) is very unreliable although attempts have been made to alter the given Madrid grid reference through a Greenwich grid reference to an ETRS89 grid reference, seen above.
The site, named by los lugareños, has not yet been located but it is apparently in the same area as site 4004.

Reference: anon., 1980a; anon., 2014b (Easter logbook)
Entrance picture :
Underground pictures :
Video :
Detailed survey : from 1980a
Line Survey :
On area survey :
Survex file :