Porth yr Ogof in Waterfall Country

This southern edge of the Brecon Beacons National Park contains a belt of carboniferous limestone wedged between Old Red sandstone to the north and the Millstone Grit containing coal deposits to the south. One of the characteristics of carboniferous limestone is that it is susceptible to the action of slightly acidic water. Rain falling in this locality absorbs carbon monoxide from the air thus creating a mild solution of carbonic acid. As this slightly acidic water passes through the naturally occurring cracks and fissures in the carboniferous limestone over geological time it has created the extensive cave systems found along this southern edge of the Brecon Beacons National Park.

Safety and Access from the Car Park:

• Porth yr Ogof car park, at the time of writing, is manned most days by an employee of the Brecon Beacons National Park. There is a car park charge of £3 per day.

• Access to the cave entrance is located just a few minutes walk from the car park.  The ascent to the cave from the car park is a very steep and as the foot path is formed from the exposed limestone rock is deeply grooved and uneven. Children should be supervised and adults should also take particular care. This foot path may not be suitable for everyone including young children, the elderly, disabled or infirm.

Porth yr Ogof:
 
Porth yr Ogof translates as the gateway to the cave. Porth yr Ogof is the largest cave entrance in Wales and one of the largest anywhere in the United Kingdom. It is nearly 20 m wide and some 3 m high. The cave was at onetime referred to as the white horse cave. The name is derives from Calcite streaks just inside the cave which resemble the head of a horse. Calcite is a crystalline foam of calcium carbonate in the same way that ice is a minimal or crystalline form of  water. On the surface to the south of the cave entrance below the minor road it is possible to walk albeit with some difficulty are longer the original riverbed of the Afon Mellte prior to its collapse upstream and submergence in the Porth yr Ogof cave system.

• Only experienced cavers and with local knowledge should attempt to explore the cave system at Porth yr Ogof. this cave system has claimed more lives than any other caved in Britain.

Further Information:  

• Caving and Safety at Porth yr Ogof 
• Caving Guide to the Brecon Beacons
• Aberdulais Falls
• Waterfall Country  
• Ystradfellte  
• Ogof Ffynnon Ddu
• Publication: "The Secret World of Porth yr Ogof" by Martin Farr Gomer Press 1998 
  ISBN 1 85902 501 3
• Caves and Karst of the Brecon Beacons National Park - a field guide, by Mike Simms British Cave research association Cave studies series No 7 1998 ISBM 0900265205.