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Porth yr Ogof in Waterfall Country

The Web Brecon Beacons
Porth Yr OgofBrecon Beacons Geology and Cave Systems:

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 dioxide 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 4 per day for Motor Cars 7 for minibus..

  • 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  very steep. As the footpath is formed from the exposed limestone rock it 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.



Brecon Beacons National Park signs warn of the dangers of:

  • falling rocks

  • deep water where people have drowned

  • caves and mines where access is suitable only for properly equipped and supervised groups with specialist knowledge of the locality.

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 form of calcium carbonate in the same way that ice is a 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) along the original riverbed of the Afon Mellte prior to its collapse upstream and submergence in the Porth yr Ogof cave system.


Caving and Safety:

Currently nearly 3 km of the cave system at Porth yr Ogof has been explored. This cave system is very popular with cavers and with groups from outdoor centres. It should be noted that deaths have occurred and that passage through the cave system should only be attempted by experienced cavers, who are well equipped, and have local knowledge, or are being led by an experienced caving instructor with local knowledge of this particular cave system. It is essential that you verify the accreditation and local experience of any instructor. Caving Guide to the Brecon Beacons

  • 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 cave in Britain.

In periods of rainfall the cave entrance and the passageways can fill with water very quickly.







Further Information:  

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(of the Brecon Beacons National Park Authority) & supports National Park aims regarding recreation, conservation & the local economy. 

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