Caves of South Wales Dragon

Twll Clogfaen

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Twll Clogfaen (Boulder Hole) starts off as an extensive dig through a mixture of gritstone and limestone boulders until it reaches a small streamway, this is then followed via two pitches to reach a lower streamway. The lower streamway is very low and is followed to an inlet emerging from and aven and then eventually to an impossibly tight conclusion.
Length 280m +
Altitude 248m
Grid SO 02250 08484
The site is one that has been dug for a good many years with Marshall Davies, Tony Donovan, Frank Longwill, Roy Morgan, Adrian Paniwnyk and friends excavating their way into this new cave, which Roy has named Twll Clogfaen.
The cave is located close to the A470 a short distance north of Merthyr Tydfil. Taking the A470 from the A465 roundabout after a few hundred metres a road leads off on the left to access some farms. A cattlegrid is passed at the junction and a short distance on the left is an area of hard standing used by peoiple accessing the local footpaths. The cave is located on the left a short distance up the stream that is culverted under the road at the point you park.
Central Northern Outcrop Google map showing the location of Twll Clogfaen and other caves in the area.
Location map - click marker to show entrance photo
The cave is located near a public footpath and is gated at the request of the landowner. The cave is accessed via a Derbyshire Key system.
A climbing descent down the most impressive of digs, through the gritstone and limestone boulders. A massive amount of well installed scaffold had gone into securing the entrance shafts. Soon the sound of a stream can be followed into cave proper and the top of the first pitch is reached. A 5 m steel ladder is in-situ aiding progress through the spray. At the bottom an area of well taped formations is passed on the right before the stream is followed the short distance to the head of the second pitch. Here the water cascades down an 8 m deep pot, and a sturdy scaffold ladder allows an easy descent. On the far side of the chamber a calcite flow cascades down the wall. At the bottom the way on is a low wet crawl (can flood in wet weather) which sets the scene for the rest of the cave. A long flat out crawl lying in water and crawling over small rocks is followed for some distance until the passage relents slightly at a junction with the main streamway. Downstream in stooping passage reaches a sump under a thick shale band. Upstream leads via some stooping and crawling to the bottom of a tall aven about 12 m tall climbed by Matt St Clair with an impressive waterfall and draught. The water enters via a too small inlet at the top. Just prior to the waterfall aven heading upstream is a passage on the left. This is tight and leads to a calcite blockage after 10 m, it draughts well and can be seen to continue beyond.
Fixed ladders are in place on the two pitches. You may wish to bring your own lifeline for these two climbs.
Cambrian Cave Registry for Twll Clogfaen
Cambrian Caving Council Newsletter 42
Descent | No.235 p16 (2013)
Below the two pitches the cave changes character to become a long, low flat out crawl in a stream. There is a serious risk of flooding of these crawls in wet weather.
The photographs and information of this page has been provided to help cavers planning trips. Caving can be a dangerous activity, if you are interested in exploring caves please join a caving club so you can enjoy a safe introduction to this sport. Local caving clubs are listed on the links page or you can visit the 'New To Caving' website for more options.
If you feel that any of the information is incorrect or should be updated please contact us.