South Wales Caves

Porth Yr Ogof Description

Porth Yr Ogof (translated as the gateway to the cave) boasts the largest entrance of any cave in Wales at over 17 metres wide and almost 5m tall, this with its close proximity to the road has made this a popular visitor attraction. The cave is accessed from a secure pay and display car park and Cwm Porth Information Centre staffed by a Brecon Beacons National Park Warden see map for location. The cave has 15 different entrances leading to over a mile of accessible underground passageways which makes this very popular with outdoor groups to introduce people to caving. In normal weather conditions a dry rocky river bed leads up to the main entrance to the cave, but following rain this may quickly become a raging torrent as the Afon Mellte (the Lightning River) lives up to its name and quickly makes the cave inaccessible, care must be taken in wet weather. Another sinister danger in this cave is the resurgence pool, where the water leaving the cave is forced through a narrow passage, in doing so it has scoured out a 7m deep pool with underwater ledges, this coupled with the strong undercurrents created by the flow of the water has made this the most dangerous location in any British cave. In this short section of cave 10 people have drowned all within the sight of daylight, the dangers here should not be underestimated, signs in the cave before the pool warn of the danger and direct you to alternative exits.
The main cave is accessed via a limestone walkway on the east side of the main entrance which leads into the large day lit entrance chamber. The large passage in the right hand wall of the main chamber leads to the Right Hand Series. A small entrance further down and about 1.5 m up the wall leads to a small passage that takes you to Sump 6. Ahead the passage soon reaches water at the White Horse Pool which is several metres deep and takes its name from the equine appearance of the white exposed calcite vein on the wall above the pool. On the left of the main chamber are five passages, the first is a large alcove. The second passage leads to a low wide chamber that connects to the Upper Stream Passage and an entrance often referred to as the Tradesman's Entrance. The three final passages on the left of the chamber all lead to the lower section of the Upper Stream Passage. The Upper Stream Passage follows downstream to Sump Five and deep water to connect to White Horse Pool. Beyond the White Horse Pool the stream passage is quite impressive with black vertical walls and deep water for over 50m. The water becomes shallower and the passage wider as the Great Bedding Cave is reached and the passages of the Right Hand Series connect to the main passage. A passage joins here on the left hand side with water issuing from Sump 10. Further downstream the roof raises by about a metre and the cave is seen at its widest point at over 35m across. A large shingle bank occupies the left hand side of the passage with the stream flowing on the right. A wade through deep water leads to entrance I on the left while following the water down a series of short rapids entrance J can be accessed over the shingle bank on the left. Following the water further downstream leads to the final lake and the route to the resurgence pool where daylight can be seen. Signs in the cave here warn against crossing the pool directing you to alternative exits.