Ogof Ffynnon Ddu, Limestone cave system in Upper Swansea Valley, Wales
The network of Ogof Ffynnon Ddu extends across 59 kilometers with passages containing underground streams, waterfalls, stalactites, and stalagmites throughout its chambers.
The South Wales Caving Club members Peter Harvey and Ian Nixon discovered this cave system in 1946, leading to extensive explorations that revealed its geological importance.
The cave's Welsh name translates to Cave of the Black Spring, reflecting the local language heritage and its connection to natural water features.
Access to the cave requires permits from the South Wales Caving Club, and visitors need specialized equipment to navigate the challenging underground environment.
At 274 meters deep, this cave system holds the record for the deepest cave in the United Kingdom and ranks as the second longest in Wales.
GPS coordinates: 51.82430,-3.66110
Latest update: March 6, 2025 13:15
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