Caves of South Wales Dragon

Ogof Tarddiad Rhymney

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Ogof Tarddiad Rhymney is located in the base of a quarry face, with a small climb down leading to an impressive sized passage. The cave is quite linear with one major series radiating from the main passage that ends as a too tight stream.
Length 1608m
Altitude 561m
Grid SO 08511 14117
Ogof Tarddiad Rhymney was discovered in 1993 by Jeff Hill and John Parker of the GOCAF in the base of the rock face in a then working quarry. It was in 1995 that the quarry ceased working on this site and the location became more widely known. The cave is quite dry throughout but carries a small stream that has been shown to resurge at a spring above the Blaen Rhymney Reservoir.
Ogof Tarddiad Rhymney (Rhymni) is located in the Cwar Yr Ystrad Quarries about three miles from the village of Trefil.
Black Mountain Central Google map showing the location of Ogof Tarddiad Rhymney and other caves in the area.
Location map - click marker to show entrance photo
No known access restrictions. The entrance is generally walled up with rocks to discourage casual visits by the general public. The entrance should be walled up again following a trip.
In the largest of the quarries stands an unworked mass of rock, and it is opposite this pillar near the base of the face that the entrance is located. The entrance is usually blocked with a small drystone wall. A drop of about 2 metres from the entrance gives access to a large fossil passage that carries a small trickle of a stream. The stream appears periodically along the length of the upper fossil sections of passage flowing over sections of the floor and the disappearing back into the boulder fill. The passage varies between 4 and 8 metres wide, is generally of walking proportions with occasional low sections that require stooping or short crawls. This passage continues for about 200 metres before a junction is met. To the right is a slope upwards to Nant Criban branch of the cave, while down to the left the main passage can be followed for about 300 metres to a boulder choke. The entry to the 10 metre long choke is obvious and found on the left hand side of the passage. After passing through a void, the exit is made by climbing up through the boulders to regain the passage. Beyond the choke the passage becomes very large, but this only lasts briefly as after 50 metres it reduces down to a small stream passage. The stream emerges from the boulders at the lower end of the passage and meanders through mud banks to enter a walking height rift passage. After 50 metres the passage becomes a comfortable hands and knees crawl that can be followed for a distance until a 10 metre section of flat out crawl is reached. Beyond this the passage continues a little larger with stooping and walking proportions until after a short section of crawling a small choke is reached. A flat out crawl through the choke regains the stream beyond, which can be followed until it becomes too tight to follow. From the choke a route up through the boulders reaches a small chamber with three ways off. The first heads back over the approach passage and closes down too tight to follow after a few metres. To the right a sandy passage - Ffordd Swnd can be followed, walking at first and then crawling until it chokes. To the left is a further route that can be followed for a distance, branching off before it chokes.
The Nant Criban branch begins as a small crawl, first over a hole in the floor and then through a low section past some straw formations before entering a small chamber. Following the hole in the floor allows you to drop into the Nant Llwyd streamway, this can be followed for a short distance upstream, while downstream it makes only a visible connection with the main passage. From the small chamber a low crawl on the right leads for about 80 metres through tight sections and over the top of tight rifts. This eventually reaches a 50 metre section of the Nant Criban streamway heading back towards the quarry, which has a few small passages near the north end all closing down after a short distance.
No tackle is required.
Cambrian Cave Registry for Ogof Tarddiad Rhymney
CavingUK description of Ogof Tarddiad Rhymney
Bodengo Passage extensions by the UBSS
The Caves of the Central Northern Outcrop | Tony Oldham
The entrance is located in a disused quarry face. There is danger of falling rocks and care should be take on the approach. Recent rockfalls are evident near the entrance.
The road beyond Trefil is a private quarry road and is gated and locked at weekends.
The area around the quarries is prone to car crime so it is better to park nearer the village and walk up to the cave.
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.