Torca del Regallon, Spain


The Ario Dream (pictorial representation based on OUCC surveys, compiled by M Bottomley). Connecting all these caves up would give a cave system with a vertical range of over 1,500 m but potential for 1,800 m + as caves further up the mountain are explored further!

The Ario Dream (pictorial representation based on OUCC surveys, compiled by M Bottomley). Connecting all these caves up would give a cave system with a vertical range of over 1,500 m but potential for 1,800 m + as caves further up the mountain are explored further!

The Ario Caves Project is a continuation of 50 years of Oxford University Cave Club’s exploration in the Massif Occidental of the Picos de Europa, and whose primary aim is to facilitate and further the exploration of caves associated with the Vega de Ario and the hydrology of Cueva Culiembro. The goal is ultimately of yielding a super deep system in excess of 1,800 m. This would be the deepest in Europe and one of the deeper caves of the world.

The scientific justification for this super deep system comes from the culmination of many years of exploration, surveying, geological studies, shaft bashing, careful GPS documentation and dye tracing. This work has uncovered many systems which, in their own right, range in depth from several hundred metres to > 1,000 m (namely C3-C4, 2/7, Xitu and Culiembro). Connecting these up is now a very real possibility, with the Verdelluenga system heading upstream into ‘blank space’ and the downstream end separated from upstream 2/7 by what should be a short sump. Downstream 2/7 currently ends at an enormous boulder choke – Choke Egbert – beyond which the main streamway appears from survey data to drop rapidly in depth over a short distance to the furthest explored point in Cueva Culiembro.

2015 expedition

The focus of the 2015 expedition was Torca del Regallon (C4), which was first explored in 1996 and 1997 and which drops into a major streamway – Underground Overdrive, believed to be the upstream continuation of the master cave found in 2/7 and which drains to Cueva Culiembro. The two major leads comprise the downstream sump (Special Agent Sea) suggested from surveys to be ~30 m from upstream 2/7, and a waterfall terminating upstream Underground Overdrive.

Paul Mackrill about to dive Special Agent Sea (Éabha Lankford)

Paul Mackrill about to dive Special Agent Sea (Éabha Lankford)

Despite a smaller than usual team size and shorter time frame of just over 2.5 weeks, the expedition was successful in the following:

  •  Re-rigging Torca del Regallon (C4) to a depth of 300 m, and re-bolting the rest of the cave to the base of the final pitch (Marie Celeste) at a depth of approximately 587 m.
  • Bolt climbing the 15 m upstream waterfall, which turned out to be 25 m to a steeply sloping ledge before continuing vertically upwards out of sight.
  • Successfully reaching and diving the downstream sump (Special Agent Sea) for approximately 50 m, with the way on still wide open.


The expedition was not without its challenges though, and work had to be done to enlarge a very tight rift at the bottom of the final pitch (Marie Celeste) which barred access to the main streamway (Underground Overdrive). In addition, the arrival of bad weather in the form of heavy rain and 80 mph winds meant only one pushing trip was achieved at the waterfall climb and sump. However, both were deemed significant and ongoing leads, and as such the cave was left rigged for further exploration in 2016.

Underground camp at -350m (Martin Hoff)

Underground camp at -350m (Martin Hoff)



Expedition members: Mike Bottomley (leader), Steph Dwyer, Tony Seddon, Phil Baker, Dave Ottewell, Helen Blyth, David Rose, Paul Mackrill, Martin Hoff, Tom Baker, Simon Jepps, Andrew Mawer, E?abha Lankford, Richard Cole, Callum Braithwaite, Ben Hudson

Text: Mike Bottomley

Download: Summary Expedition Report | Full Expedition Report


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