Tresviso 2022 Expedition Overview

Eastern Massif, Picos de Europa, Northern Spain

Tresviso 2022 Expedition Overview

Tresviso 2022 

Eastern Massif, Picos de Europa, Northern Spain  

1st September 2022– 20th September 2022  


 Overview & brief history:  

 The Picos de Europa is a range of mountains 20km inland from the northern coast of Spain, forming a Westerly extension of the Cantabrian Mountains.  It consists of three main areas, the Western, Central and Eastern Massifs.   

The Western Massif is to the west of the Rio Cares and has been explored by a selection of clubs including Oxford University Caving Club (OUCC), Seccion de Espeleologia Ingenieros Industriales (SEII), York University Cave and Pothole Club (YUCPC), Sociedad de Espeleologia Geologicas (SEG) and Speleo Club de Paris (SCP). This now includes the area under exploration as part of the Ario Caves Project. 

The Central Massif is between the Cares Gorge and the Rio Duje and has been mainly explored by the Speleo Club de Seine (SCS). 

The Eastern Massif is to the East of the Rio Duje.  Lancaster University Speleological Society (LUSS) were exploring the Eastern Massif from the early seventies to 1987 with the help of SEII.   


It was the Eastern Massif (or Andara) that drew the attention of LUSS in the early 1970s.  In the early years exploration was mounted from the mountain village of Tresviso and exploration was dominated by the resurgence cave Cueva del Nacimiento (Cueva del Agua) located at the foot of the mountain range.  The resurgence flows into a canal that contours the Urdon gorge with an average flow of 2 m3/s and the cave behind the resurgence leads to >12 km of surveyed passage and a height gain of over +534m.  The catchment is some 40 km3 and includes caves such as Torca Jou Sin Tierre (CS-9) at -1203m deep and Torca del Cueto de Los Senderos (Sima 56) at -1169m deep. 

 In the late 70’s LUSS pushed Cueva del Nacimiento to around the 11km and +300m mark, but after several years the cave was abandoned as all the major routes sumped and no continuation could be found.  LUSS then turned their attention to the Andara region higher up the mountain range and sought caves that would drop into the Nacimiento system and hopefully create a record-breaking >1500m traverse. They found several deep caves around this ‘top camp’ area; Sara, Tere, Flowerpot, Dosser’s Delight and Sima 56 were all pushed to respectable depths, but a connection remained elusive.   

 The discovery of newer and deeper systems, plus improved GPS, have changed the figures slightly but a connection between the deep potholes and resurgence would create; a cave in the top 10 worlds’ deepest, deepest in Spain and potentially the deepest through trip in the world.  

Top Entrance 



Current Depth(m) 

Vertical Range (m) 






CS-9 Torca Jou Sin Tierre 

Cueto Senderos 




S-33 Torca de la Hendida 





Sima 56 Cueto de Los Senderos 

Cueto Senderos 




T82 Karen – 2.6 Sara 





T145 – Pozo Castillo 





2.24 Tere 

Sara / Grajal 




FT39 Compromisso 





T169 Flowerpot 

Pico Boro 




T173 Dossers Delight 

Pico Boro 




T190 Septrin 

Pico Boro 




3.2 Fallen Bear 





T510 Cueva Entre Cuetos 

Sierra del a Corta 




T69 – Pozo Motilla 

Sierra del a Corta 




Table: Potential depth if connected to Cueva del Nacimiento +470m (2020). 


Expedition Dates 

 ·         1st May 2022 to 8th May 2022 – preliminary trip  

·         1st September 2022 – 20th September 2022 – main expedition dates 



 The expedition has several goals.  The following are a few primary objectives: 

 Cueva del Nacimiento 

 ·         Jurassic World – Barney – Leo’s Blowing Hole, draughting lead 

·         Pina Colada Bypass – calcite aven to climb?? 

·         Joe’s Crack – continuing shaft behind Death Race camp. 

·         Teeth of Satan – Wet Aven – +30m aven with draft and calcite squeeze, requires enlarging. 

·         Dan’s Big Room – unexplored section of maze in area of Dan’s Big Room and Winter Gardens 

·         Scrambled Egg Chamber – avens and leads above the Far Upstream Sump  


Cueva de la Marniosa 

 ·         Beyond Sump 2 – undescended 6m pitch (dependent on divers’ availability) 

·         Alien Weaponry – 35m aven unclimbed 

·         300m unsurveyed near Stalagmite Chamber 


Sistema Sara 

 ·         Rigging / re-exploration of system ready for dive of sump 


Secondary Objectives: 

 Time and resources permitting there are several secondary objectives that will be attempted:  

Sistema Castillo 

A large mine and natural cave complex in the Minas de Mazarrasa area.  Pozo del Castillo series was explored to -292m depth in 1983, with either a howling draft or roaring waterfall beyond a constriction at the limit.  The potential of the cave is significant but currently a collapse prevents getting to the end. Pozo Natacha series ends at -309m depth and is close to the same point in Castillo

 ·         Pozo Del Castilloshoring and bypass of rock collapse  Castillo remains a major lead, if we can get past the blockage!  In 2018 the snow level had dropped and possible to get into the next section. 

·         Pozo del Castillo – other entrances.  FT16 entrance snow plug would appear to be the same blockage in lower Castillo passage.  Snow plugs are reported further into the cave, so another entrance must exist! 

·         Pozo del Castillo surveying of Natacha upper series and locating possible surface entrance, 


Valdelafuente / Sobra Valley 

·         Re-locate draughting surface entrance on Valdelafuente, close to 80m aven beyond Sump 1 in Cueva del Marniosa, 

·       Valley above Alien Weaponry 


Sierra del a Corta  

Above the furthest reaches in Nacimiento is the Sierra del Corta.  A heavily wooded area with a number of promising leads, that could potentially drop into Nacimiento and provide an easier route into the back-end to aid exploration at the far reaches. 

 ·         T554large 100m shaft on the Sierra del a Corta, this requires some digging at the bottom, 

·         Al2a drafting shaft not yet bottomed.  Jurassic World in Nacimiento appears to be heading directly towards this site, 

·         T294 Oh What Pot (La Gobia) – continuing passage, 

·         Surface prospecting close to vicinity of Terror Firma in NacimientoTerror Firma is only 40m vertically and 200m horizontally from some parts of the surface in the Sierra del a Corta region. 

·         East of middle camp – wooded area with no sites logged 



·         Locate and descend FT43, this draughts strongly.  It is almost directly above Boulder Chamber in T87 Mazarrasa and would provide bypass to collapse at T87 entrance. 

·         Prospecting on Hoyo Oscuro and Hoyo Evangalista.  Highest entrances on the mountain range. 

·         Mine 2.32a – there is large unexplored level (with tram lines) leading to unexplored passage. 


Further Reading 

·    Expedition reports

·         Bibliography

·         Survex data set

·         Surface location map