The cave has got a lockable front door and is partially carpeted

Estate agent spokeswoman

David Jones, manager of estate agent Andrew Grant, said: "I can't imagine anyone would want to live in Rock House permanently but it could be... a very unusual holiday home."

The estate agent has received three firm bids for the property, two of them in excess of the guide price of �10,000.

A Birmingham family has owned the cave, one of up to 50 "built" in the area in the late 18th century, for more than 100 years. It is used as a retreat by the family.

Literature advertising the cave highlights its off-road parking and approximately 1.27 acres of woodland.

A spokeswoman for Andrew Grant estate agents said: "There are in fact two caves, but one is derelict and the other was last occupied in the 1950s.

"The cave has got a lockable front door and is partially carpeted. But there are no amenities.

Curiosity value

"You can't do anything with the cave because the council has said it can't be developed.

"The price reflects curiosity value. It is such an unusual thing and there is nothing like it on the market."

Bids for the unusual dwelling, hewn out of a sandstone hillside, must be in by Friday.

"We don't want to get into a Dutch auction so people interested can only make one bid," she said.

She added one of the bids had come from a woman who wanted to use the cave to get away from the "hurly-burly of city life".