Ogof Craig a Ffynnon

The cave was discovered in 1976 by Jeff Hill, John Parker and Bill Gascoine, who had been searching for years for the way in to an underground system that they knew existed to account for the water which resurged in the locality, giving its name to the Rock and Fountain Inn on the road below. The entrance is at the bottom of a quarried rock face in the disused Daren Ddu Quarry, in the flanks of the Llangatock Mountain.

The cave is about 7 km in length and is renowned as one of the best-decorated caves in Wales. It contains some early short crawling sections (and what is known as an arduous and uncomfortable boulder choke) and wet passages with voluminous quantities of mud before developing into a series of large sections lavishly decorated with mud and calcite formations. The most spectacular of these is the Hall of the Mountain King, a large cavern adorned with flowstone. The Promised Land is a long, linear passage section with a small stream.

The cave can be approached from just above the old Rock and Fountain Inn on the Heads of the Valleys Road where there is a blocked layby beside some lime kilns. An old tramroad track leads from here to the Darren Ddu Quarry. The entrance to the cave is at the foot of a rock face and is barred to prevent casual access and vandalism.