Britain's third longest caveat 50km + as well as being the deepest at -308 m . The trip top too trough trip is also the deepest through trip in Britain at -228 m. O.F.D. is a very complex cave, formed on several levels and tree destined sections, The cave is decorated throughout with many different styles of calcite decorations of which the most well known are the 2m high columns. The cave has five entrances allowing for several through trips. access is controlled by the South Wales Caving Club with a leader system in place for the bottom section (O.F.D. I).
