This is one of the two entrances to a series of man-made tunnels in the local sandstone outcrop. There is also a vertical shaft inside which reaches to the surface, although the main route in is via one of the entrances. The origin of these tunnels is uncertain.
Uploaded to Geograph by M Etherington on 15 March 2003
Photo © M Etherington, 15 March 2003. Licensed for reuse under this Creative Commons licence