Currently featured on the BBC website,

"A terraced cottage with its own underground cave has gone on sale with an asking price of just under ?200,000."

Another of those underground caves. The overground type are so rare - it'll be of great interest when the exploration of one is reported.

Although if its in a terrace, its unlikely to be 'its own', I think they call them 'cellars' ----?

For overground caves, refer to Ludchurch, a fine gritstone fissure marked on O.S. as a cave....(COPD)

Details here http://www.shropshirestar.com/news/2016/01/20/pillars-and-a-cave-bridgnorth-cottage-is-a-real-work-of-art/imgid18042654/

Bridgnorth is on soft sandstone and has a long history of caverns being mined out for storage
Or even blowing up the castle!