Tresviso Caves Project

Tresviso Caves Project Gazetter

T56: Sima 56

(Torca del Cueto Senderos, CS-1, Three Second Hole, Torca 56)

Area:Cueto de los Senderos
East, North:359775, 4785485 (nearby)
Coordinate Quality:GPS
Long, Lat:-4.7262242664832, 43.209099877596 (map)
Elevation (m):1975
Length (m):5620
Depth (m):-1169
Active Lead:
Survey Available:


on the south side of Pico Boro, west of Caseton de Andara, 50m above the red-tipped cairn


Obvious shakehole, Entrance is at bottom and under wall Entrance


A full description of Sima 56 and general information on the Tresviso/Andara region is available in the LUSS publication Sima 56, edited by Dave Checkley, Howard Jones and Steve Foster.

A short climb down a 3m pitch at the entrance leads straight onto the top of a splendid 122m shaft (Tigger's Pitch) At the bottom a roomy passage leads to a boulder choke, a way through the choke is via a series of small, interconnected chambers in rock and clay impregnated with yellow calcite (Fool's Blende Passage).

Beyond Fool's Blende Passage a large chamber with a pitch at the far end is reached. This is a broken descent of 47m down a wide rift and onto a mud bank. Here is a junction with two inlet series, uniting at several levels. The floor of the junction, known as T-Junction Cafe, leads to another 17m pitch down. The way on is a meander, very narrow at first with two upward squeezes but then widens a little. A climb down at the widest section, Short Arses' Dilemma, leads to another junction. The right-hand fork ends at a sump (un-dived)

The left-hand route continues down a 4m climb into a rift over jutting shale bands to another short pitch into a chamber. Some very large and very unstable blocks are perched at the top of this pitch (now fallen?). The pitch is 4m to a chamber, The Abattoir, which has an active inlet entering on the left and a small stream disappearing down the rift continuation on the far side (N.B. Water tracing conducted here reappearing in Cueva del Nacimiento.)

This section is very strenuous, especially with tackle, and is traversed for 110m past several inlets to a pitch back down to the water. In several places the wall is covered with sharp calcite crystals (The Slasher). After the Slasher a 14m pitch lands on a shelf 6m above the stream, a meander is followed at various levels, up a 7m climb, along, down a 12m pitch, down a 4m climb, sometimes in the water, but generally above it. A large chamber is reached (Bernie's Cafe), beyond, the water sinks down a 31m pitch.

Below is a confluence with a choked inlet, discharging a larger stream than the one followed up to this point. Further downstream the nature of the cave changes and the roof descends to the top of the 23m Pink Pitch. This shaft is completely enclosed with beautifully fluted walls and the stream disappears down a small tube at the bottom. The tube leads almost immediately to a small pitch. The pitch can only be rigged from here, but directly in the water. 5m down a sloping shelf gives a dry alternative but requires a precarious pendulum under the full force of the water to reach it before. At the bottom of the dry alternative (a pitch of about 15m) a short passage leads back to the wet pitch. (Far Canal). Climbing up the rift just before Pink Pitch leads to a huge parallel shaft which is a superb free hang for 118m to a wide ledge and quickly followed by a 24m pitch to the floor of the shaft. At the top of the 24m pitch a small window gave a tantalizing view of a spray-filled parallel shaft.

The water at the bottom is the same water last seen at the Far Canal. The water exits along a small rift and down a hole in the floor. Traverse of the top and down a 9m ladder climb. The stream cascades down a steeply inclining phreatic passage. At the bottom is a miserable looking sump with a narrow rift above that has defied several attempts to get through. (depth -492m)

Above the 31m pitch, after Bernie's Café, is a large phreatic passage that splits into three ways on, all of which are entrances to the same complicated maze. Main route is through a 15m high rift passage. 10m further on is an aven, a sandy depression in the floor and a 3-4 m wide inwardly draughting phreatic tube on the far side. The tube is quickly followed to the head of a short pitch. This pitch is 8m followed by one of 15m into Humbug Hall.

Humburg Hall is a large elongated chamber in dark limestone with white mineral veins. Numerous huge boulders litter the floor. Between the largest of these (The Humbug) and the left hand wall a rift passage leads off. br>
Note: Camp 1 usually set up in Hamburg Hall

The water sinks down a pitch of considerable depth but traversing along leads to another pitch of about 60m. At the bottom is a very narrow meander to a pitch of 8m. The rock is extremely brittle and dangerous. The passage is not surveyed, nor has it ever been returned to. (Death Wish Pitch?)

Above the 60m pitch it was possible to climb into an old 4m wide phreatic roof tube. The rock is brittle here and care is advised. After 50m the tube divides, both branches ending at pitches.

The left branch leads underneath back to the 60m pitch, just passed the pitch (?) is a 15m pitch (Death Wish Pitch)

The right-hand route descends pitches of 7m and 19m to a large canyon-like passage. This passage is also unpleasantly loose. After about 50m of careful traversing a point is reached where it's possible to climb down for 20m but the floor is still below and not reached. It is also possible to climb up instead of down and after two 3m ascents large chamber is met. Up the boulder slope on the left the roof closes down but another pitch is encountered (more or less over the top of the unfinished 20 m climb).

The pitch at the top of the boulder slope is 24m into a large canyon passage, with winding meander below. The direct route down the canyon is very loose and dangerous so instead continue along and down a hading rift, Lavatory Pan Alley, before finally popping out through a very narrow section to a 3m pitch down to a balcony. A 12m pitch leads back into the canyon.

The most obvious route leads to pitches of 11m and 16m, followed by a number of climbs up and down finally reaching the stream way. Following a narrow rift below the 16m pitch another 13m pitch is encountered and the stream way re-joined again. After two more pitches of 10 m and 9m the stream way narrows and the water cascade down a 3m climb into the start of yet another narrow meander. (The Crumbles). Follow the meanders for 150m to a chamber and then a wider continuation of the meander.

The high-level continuation is very loose and nasty so taking the middle road, leads to a climb down in the rift to a 29m pitch in a dry shaft.

The water sinks down another pitch further back in the rift to take a different course of its own. The only way out from the bottom of the 29m shaft, is another meander, tight and awkward at the bottom. It is possible to climb 11m up the shaft and over the top of the meander to an 11m pitch into a small chamber. Further traverses and a 16m pitch leads back to the stream way again. (possibly same one as the one seen in the Crumbles but not known) Traversing in the roof for around 50m leads to climbs of 10m and 4m back to the water and to the head of the split 19m Cascades Pitch.

Note: Several of the pitches between Lavatory Pan Alley and The Crumbles as pitch as the Cascades Pitch gets very wet and unpleasant, not to mention potentially dangerous with a couple of day's rain.

A large boulder strewn chamber makes pleasant change from the ever present meanders. Clambering over boulders and down several climbs a 29m pitch into another chamber is met. A short rift, a 12m pitch and suddenly the cave closes to a wet 40m crawl in a miserable little rift. (The Wrectum). A pitch of 19m leads to a moderate sized chamber. Another pitch of 12m enters a 150m long phreatic section, containing several creamy white stalagmites and flowstone coated with deep red calcite. (Dripping Blood Passage).

Note: Camp 2 is usually located here, approx. 12 hours from entrance when rigged.

The stream disappears at a small sump at the beginning, reappearing at various intervals leaving a dry-floored tube. Dripping Blood Passage ends with a 6m pitch into a pool on the floor of a chamber. Straight ahead the water drops down a 36m deep shaft and subsequent 8m pitch. More meanders are encountered this one can be traversed for 70m at varying levels above the floor to a 10m pitch back to the water. The stream sinks into the floor here.

A further 65m of traversing ends with a 38m shaft with the way on over the top of the shaft.

The 38m shaft enters more meanders, The Grand Canyon. The rift is followed for 70 m, up a climb, along, down a 7m climb, down a 6m pitch, along and down a 10m pitch. The passage closes down briefly to 1m high, opening up again almost immediately beyond. A rift becomes too tight but a strong draught is evident and rushing water has been heard (depth -817m).

In the Grand Canyon between the 6m and 10m is a climb down to a 5m pitch with a duck beyond, a miserable affair in dry gear. There are two more pitches of 5m and 7m followed by a 100m long walking-sized passage to another impassably tight rift.

Well above the top of the 38m a traverse line needs to be rigged, the Nylon Highway. A climb down for 20m on the far side reaches the floor of a rift whose walls are encrusted with tiny aragonite crystals. After 25m a 5m climb down to Pozo Aragonito, an 11m pitch similarly decorated with aragonite. The rift continues at the bottom, Meandro Rojo y Blanco, well decorated with white calcite walls and a dark red calcite floor. 40m along, it ends at Pozo Rojo, a 39m pitch with dark red flowstone near the bottom.

Three short climbs down lead to an 8m pitch, followed immediately by another of 14m with a deep red calcite flow down the face of the pitch. A colourful 70m section of narrow fossil stream way is heavily decorated with red and white calcite and numerous pools along the floor. The Rio Rojo, ends as a 5m pitch into a deep pool, requiring an awkward pendulum at the bottom to stay dry. A short rift follows and then another pitch.

The Betelgeuse series is entered by climbing up to the left from the bottom of the Rio Rojo pitches, up some loose fill and around an awkward step to the left onto some chocked boulders. This leads onto a steeply descending passage, The Hyperspace Corridor, between the wall on the left and huge, square cut boulders, on the right. It is possible to crawl over the top of these boulders up a sloping slot until you get frightened.

Following the Hyperspace Corridor down you pass down a straight sided passage and then enter a more irregular passage with boulders on the floor. At the end of this passage are 3 bolts on the left, giving a good hang onto a pitch, 29m to a ledge with an incised canyon and another 12m pitch. Part way down the P12 is a large wedged boulder that resisted efforts to move it, but still seemed a little daunting. It was named the Great Collapsing Hrung Disaster. Past the 'Hrung' the next pitch is again belayed on the left to give a terrific free hang for 13m. As you near the floor on the 13m pitch there is a hole in the calcite wall in front of you, which leads into a sharp calcited rift passage with chocked boulders. From this rift it is possible to climb down with care to a beautiful calcite chamber, The Evildrome Boozarama, from which it is possible to rejoin the main route.

From the bottom of the 13m pitch a rift leads right, which merely provides an alternative to the pitch below. The way on is down the calcite slope on the left, by two pitches of 10m and 13m respectively. Near the bottom of this P13 is a bolt change, next to a 3m long straw dubbed PMI. From the bottom it is possible to go left and up a slippery climb of 1.5m into the Evildrome Boozearama, which is well worth a visit and is very entertaining to get out of safely. The calcite floored chamber at the foot of the second P13 slopes muddily to a rift on the right, which was too slippery to get into but did not appear to go anywhere. To the right of the rift a P17 (awkward to rig). From the base of the p17 a traverse to the left descends a muddy P10 and P7, using small stal. belays. There then follows a rather muddy section with a P20 and P9 on muddy slopes into the large chamber before the Rib Tickler. This chamber is also entered by the 17m pitch from The Forest, and so is the junction with the old 1983 route. The whole of the top part of the Betelgeuse Series is very pleasant, with calcite and lots of decorations, whilst the bottom part is very muddy and awkward. There is a distinct change from one to the other at the Evildrome Boozarama. The whole series seems to be a very much nicer alternative to the old route of The Forest and Aberfan.

The pitch is 10m deep and is followed by another of 9m. 20m further on the cave begins to descend rapidly in staircase fashion. First a 2m climb then, a 4m pitch, and then another nasty 3m climb down. Seven more pitches of 8m, 7m, 5m, 15m, 4m, 6m and 1 m follow in quick succession.

At the bottom a 3m pitch leads to a slope down to a 3m climb. This is followed by a 30m long calcite rift and then a small hading rift ending at successive pitches of 2m, 8m and 17m.

A muddy rift passage with a slippery sloping floor leads to two awkward climbs down before entering a phreatic section lined with mud but still taking a discernible draught. A 3m climb down is followed by a hands and knees crawl through a small tube to a 3m climb up with a 3m climb down on the other side.

The only way on is a narrow slot in the floor, The Rib Tickler. A pitch of about 5m leads to a 3m wide by 8m high passage, descending at about 60 degrees for approx. 90m. This is the F.U.Z.2 ramp.

Ascending up the F.U.Z.2 ramp, Wowbegger the Infinitely Prolonged, for 60m (rope required for descent), leads to ledge and a blind pot, The Total Perspective Vortex. Water enters from two inaccessible holes in the ceiling. To the left is the Frogstar B Series. The series was not surveyed but it is on the same plane as the Wowbagger - F.U.Z.2 ramp, and is a similar sort of rock. However, it has developed pitches and pots and is covered in the mud which is seen at the sides of the ramp. It also has quantities of the odd white pebbles which litter the scallops in the ramp. A series of pitches and chambers proceed down, on the same general plane as the ramp, and become smaller and trend beck towards the ramp. They probably join up with it again, but never established

Continuing down the F.U.Z.2 ramp leads to two routes. The first begins with a 12m climb and then a 10m pitch to the head of a 4m climb. At the bottom is a 9m pitch straight a huge sump pool. The second route meets the same fate, a 15m pitch then 20m pitch into the same sump pool (depth -1169m).

Notes on hydrology There are at least three separate stream ways in the cave. The first stream (dye-tested to Cueva del Nacimiento) begins at the Abattoir and is followed for most of the stream to the 1979 terminus, the sump at -492 m. Numerous inlets feed the stream but even during wet periods it is not particularly large. Above the P31 an older phreatic section of the cave is entered, leading to Humbug Hall. Here another small stream enters via an even inlet and sinks down an undescended pitch. The water is presumably, but not necessarily, that which is encountered at the bottom of the P60. The latter has been followed for some way but not to a conclusion. Exploration has been concentrated on an upper phreatic level with subsequent vadose development for up to 60m below it. The roof is eventually lost at P24 where the direction of cave development changes by almost 90 degrees. The next section is a steeply descending canyon-like passage and after several more pitches another active stream way is reached. This water rises above the level of the sump at -492 m and is therefore a separate stream from the first, but may be fed from the water below P60. Presumably it is the same stream which is followed all the way to Dripping Blood Passage although the water is temporarily lost for the three pitches which follow the Crumbles and also just before the Cascades Pitch. The stream does not increase appreciably in size during its visible course and is finally lost just before the P38, the parting of the ways between the Grand Canyon and the 1983 discoveries. The rift passages from the far side of P38 to the top of F.U.Z.2 are mostly dry although standing pools in the Rio Rojo suggest that a stream may flow here during periods of high rainfall. The water in F.U.Z.2 is considerably larger than anything else in the system following rain. This stream is probably distinct from the others in the cave. The significance of 56 as a drain for the surrounding area is obscure. The position of the massively developed entrance series, right under the main ridge separating the Ceuto Senderos (Sima 56) and Pozo de Andara (Pozo de Andara (Lake Depression)) suggests that the surface topography must have been very different at the time that the cave was formed. The general horizontal trend of cave development in Sima 56 is Northwest, similar to T169 Flowerpot and 3.6 Sara. Although the cave is 2.6 km long, the far end is only 0.5 km closer to the upstream sump in Cueva del Nacimiento than the Sima 56 entrance. The task of joining these two caves is formidable if not an impossible one, with nearly 4 km still between them. There is, of course, no certainty that the passages beyond the first stream way in Sima 56 will eventually head towards Agua at all, nor can we be sure of the fate of the water in the latter part of the cave. However, the sump at -1169 m is already below the level of the Rio Duje where it passes Sotres, and Cueva del Nacimiento is still the nearest of the possible resurgences.


L.U.S.S. (1974-1977)
LUSS and SEII, Sima 56, Madrid, 1985
Also see Caves and Caving No. 9, No. 19, No. 28 and No. 31.
P. Benoit, et al; "Les Picos de Europa"Spelunca, suppl. At No. 19, 1985, pp.48-49.
C. Puch, op cit .., 1981, PP27, 69..
SWCC (2009-2014)
Tresviso Caves Project (2015-2017)
S.E.I.I. (1984). "Memoria de la campana de verano 1983. Macizo de Andara, Tresviso, Cantabria". 13 pags.
Martinez, F. "La Sima 56, nuevo record de profundidad en Canta-Sima del Cueto de los Senderos.
Anon.. (1978). "List of Caves". En "LUSS. Expeditions to Tresviso and the Picos de Europa in northern Spain 1974-1977". Pp. 34-66.
Checkley, D. ; Jones, H. ; Fostes, S. (1985). "Sima 56, Picos de Europa, Espana". L.U.S.S. - S.E.I.I. Edicion bilingue de la Univ. Politec. Madrid.
La participaci'n de la S.E.I.I. en esta y otras cavidades de Andara es consecuencia de la aplicacioon de una nueva politica en la distribucion de zonas de trabajo por parte de los responsables de la Coordinacion de Actividades Espeleol'gicas.
Sefton, M. (1978). "Tresviso 78. An expedition to the Picos de Europa, northern Spain- LUSS 1978". Pag. 36, 50.
Anonimo. (1980). "Tresviso 79". LUSS. Pag. 16, 17, 34, 35.
Anonimo. (1980). "Tresviso 1979". Jumar-4:20-30.
Sefton, M. (1980). "Tresviso '79. An expedition to the Picos de Europa". Caves & Caving-9:12-15.
SEII. (1982). "Expediciones a Tresviso". Cuadernos de Espeleologia-9/10-183-214.
McKee, H. (1980). "LUSS expedition pushes Picos 56 Pot to a depth of 1,615 ft". Descent-44:21-25.
Anonimo. (1981). "Tresviso 80. An expedition to the Picos de Europa, Northern Spain, 1980". L.U.S.S. Pp. 13, 16-17.
Anonimo. (1983). "Tresviso '82. An expedition to the Picos de Europa, northern Spain, Summer 1982". L.U.S.S.-S.E.I.I.
Checkley, D. (1983). "Tresviso '82. An expedition to the Picos de Europa in N. Spain". Caves & Caving-19:28-29.
Anonimo. (1985). "Sima 56". En "Les Picos de Europa". Spelunca supl. Du no 19:48-49.
Jones, H. (1984). "Tresviso 83. Further Exploration in 56". Caves & Caving-23:15.
Jones, H. (1985). "Tresviso 84. 56 and the year of the dosser". Caves & Caving-28:21-25.
Sefton, M. (1984). "Cave explorations around Tresviso, Picos de Europa, Northern Spain". Cave Science vol. 11-4:199-237.
Puch, C. (1984). "El Pulso de las exploraciones". Exploracions-8:121-127.
Ibberson, P. (1987). "Exploration of 56, 1984-1985". LUSS-4, vol. 2 no1:45-48.
Iles P. (1987). "Tresviso. Betelguese Series, Sima 56; Frogstar B Series, Sima 56". LUSS-4:50-52.
Puch, C. (2002). Torca del Cueto de los Senderos. En "Grandes Cavidades de Espana con mas de 1000 m de desnivel".