Eastern Massif, Picos de Europa, Northern Spain

In 2019 the Tresviso Caves Project continued work in Cueva del Nacimiento, Cueva de la Marniosa and ongoing work on the Andara mountain range.

The Club d’Espeleologia l’Avern Ontinyent (CEAO) also continued work in the Portudera region (Asturias).

Tresviso 2019 (TCP)


The 2019 expedition was undertaken with collaboration between numerous UK based caving clubs and the Spanish AD KAMI club, under the banner of the Tresviso Caves Project.

As per previous year’s most of the work was concentrated on two main caves, close to the village of Tresviso.

Firstly, Cueva del Nacimiento, a >13km cave system with a height gain of over +535m from the entrance.  The catchment of this cave totals 37 km2 and, if linked with known cave systems high in the Andara mountain range, would create a potential >1500m deep underground traverse, one of the deepest in the world.

The second main cave of interest was Cueva de la Marniosa, slightly further up the valley and a feeder system into Cueva del Nacimiento.  On the 2018 expedition a new entrance to the cave was discovered, creating a -423m deep through trip.  A side objective of the 2019 expedition was to attempt this first through trip.

In addition, the ongoing re investigation of some of the caves on the higher Andara range was continued.


The 2019 expedition has continued to build on the successes of previous trips advancing exploration in line with objectives and discovering over 1.5km of new cave and several new leads.  Over 2km of existing cave was also resurveyed to improve accuracy of old data and provide a better picture of the interconnected systems.

Cueva del Nacimiento

The Parting Friends sump was successfully dived during the expedition. It took 3 days to rig and re-survey the route to the sump, before the dives could be attempted.  Over 400m of new passage was discovered, covering 3 sumps and a 4th un-dived sump.  The new sump was proven to follow the main Nacimiento route through the mountain, but at a lower level, and is the same water as seen at the Far Upstream Sump.

A trip to Dan’s Big Room, to investigate the unexplored maze, was undertaken but time and route-finding issues prevented any progression in the area.

As part of the Parting Friends dive, the preceding Road to Wigan Pier streamway, from the Black Hole, was re-surveyed to BRCA grade 5 standards, replacing the previous 1986 grade 2 survey.  This work will be continued in 2020.

Likewise, the Outer Mongolia passage, leading away from Clapham Junction was resurveyed, with a few potential leads confirmed.

Cueva de la Marniosa

In the Extra Caverns Series, several leads were explored.  The Free Willy Aven was aid climbed to a height of 23m across 3 separate avens, the first one becoming impassable, the second one leading to a further unclimbed aven and the main aven still continuing, but with a possible lip to the aven in sight, a further 10m higher.  This will be revisited on the 2020 expedition.

At the southern end of the series, two small avens were climbed to a continuation into Forgott Passage.  23m of passage leads to two more unclimbed avens.

During a surveying trip a large void above the main streamway was scaled and entered the large Alien Weaponry chamber.  Not shown on any previous surveys, this chamber was a significant find, over 100m x 50m x 25m in dimensions and multiple leads discovered.  Similarly, below the entry point to the chamber a new inlet streamway was discovered.  Again, this is not on any survey and appears unexplored.  The passage was named The 42 Streamway (for the closest surveying station) and heads south into the Valdelafuente ridge.  These will also be major objectives of the 2020 expedition.

In Cueva de la Silvestre, an unexplored dry lead near the entrance series was extended for 62m to a boulder blockage.  Bob’s Crusade Sump was dived for 32m to a potential tight diggable lead and the Wet Willy Sump was passed after 3m to 40m of streamway and a second 10m sump to a tight continuation

T20A Cueva de la Silvestre – Cueva de la Marniosa through trip

Cueva de la Silvestre was rigged on the first day of the expedition and the first through trip was undertaken the following day.  A team of 4 completed the trip in just under 6 hours.  One further through trip was completed before the Silvestre side of the trip was de-rigged.  After 41 years of exploration, these were the first subterranean traverses of the mountains in the area.

The overall cave system is now 6,300m long and -423m deep (from the Silvestre entrance to the furthest point beyond sump 2 in Marniosa).  It is now the 2nd longest and 10th deepest cave in the Tresviso – Andara region.

Minas de Mazarrasa

T145 Pozo del Castillo was revisited, following the passing in 2018 of the snow-plug that had blocked the route down into the cave since the 1980’s.  Unfortunately, further collapse has blocked the way once again.

T145 Cuesta was explored further, passing an old wooden bridge across a large pitch.  The passage beyond and the lower levels were explored and resurveyed.  Although a few sections were unexplored, potential appears to be limited.  However, in future an attempt will be made to enter the cave via the higher T123 ROSA entrance to explored and complete a fuller survey.

Several other old mines were revisited, including T144 Rosario and T436 El Queso.  In both cases no previous survey existed and a new BCRA grade 5 survey was commenced for both.  T436 El Queso has now been shown to pass within 5m of passage in T145 Pozo del Castillo.  Examination of the surrounding area is recommended for future trips to look for potential ways past the snow blockage in Castillo.

Sierra del a Corta

Several leads were identified and T48 La Torca Grande was revisited, but unfortunately still contains a large snow plug preventing further progress, despite there being very little snow compared to previous years.


As per previous expeditions several old sites were revisited and cataloged, plus several new leads for future trips were identified.


Alastair GottTechnical Speleological GroupUK2019Tresviso 2019
Arwel RobertsSouth Bristol Speleological SocietyUK2019Tresviso 2019
Bob ClaySouth Bristol Speleological SocietyUK2019Tresviso 2019
Derek CousinsLancaster University Speleological SocietyUK2019Tresviso 2019
Howard JonesLancaster University Speleological SocietyUK2019Tresviso 2019
Joe DanielsIndividualUK2019Tresviso 2019
Leo BradleySheffield University Speleological SocietyUK2019Tresviso 2019
Lisa BooreChelsea Spelaeological SocietyUK2019Tresviso 2019
Lydia Clare-LeatherSheffield University Speleological SocietyUK2019Tresviso 2019
Phil WalkerBradford Pothole ClubUK2019Tresviso 2019
Rob MiddletonBradford Pothole ClubUK2019Tresviso 2019
Stuart CoxonBradford Pothole ClubUK2019Tresviso 2019
Toby DrydenSouth Wales Caving ClubUK2019Tresviso 2019
Will BurnSheffield University Speleological SocietyUK2019Tresviso 2019

Documents & Links


BPC Bulletin Vol 7 No 7 21 MB 13 downloads

Summary of Tresviso 2017-2019 ...

Tresviso 2019 5 11 downloads


    Bejes 2019 (GE Flash & CDE Tracalet)







    Documents & Links


    Bejes 2019 27 MB 7 downloads

    GE Flash & CDE Tracalet ...

      Portudera 2019 (Club d’Espeleologia l’Avern)


      Since 2016 Club d’Espeleologia l’Avern de Ontinyent (Valencia) have been exploring the area of Portudera in the Eastern Massif. The project aims to catalogue and explore the caves in this area


      Multiple sites located and explored, exploration ongoing


      Vicent SanchezClub d'Espeleologia l'Avern OntinyentES2019Portudera 2019
      Rebeca DiazClub d'Espeleologia l'Avern OntinyentES2019Portudera 2019

      Documents & Links


      Memorias Portudera 2019 5 MB 10 downloads