Ogof Ffynnon Ddu (Welsh for Cave of the Black Spring; also known as OFD) is a cave located under a hillside in the area surrounding Penwyllt in the Upper Swansea Valley in South Wales. At 308 metres deep and 68 kilometres long, it is the deepest cave in the UK and the second longest in Wales. Read more
Spoiler
A new video by Keith Edwards highlights the Fault Aven area of Ogof Ffynnon Ddu, the deepest cave in the U.K. and the second longest in Wales. Read more
Dan yr Ogof, also known as the National Showcaves Centre for Wales, is a 17-kilometre long cave system in south Wales, five miles north of Ystradgynlais and fifteen miles south west of Brecon within the Brecon Beacons National Park. Read more
The Dan-yr-Ogof cave system was discovered on 21 August, 1912.