Wookey Hole Caves are to be opened at night for the first time in the history of the Somerset tourist attraction.
The caves' owner wants to know if they are haunted
It is part of a drive by their new owner, Gerry Cottle, to widen the appeal of the caves and to find out if they are haunted.
The attraction is steeped in stories of paranormal activity and ghosts.
When the cave complex opens for its first 'spook night' on 7 July, visitors will have a chance to experience any unusual phenomena for themselves.
The cave's most famous legend is the Witch of Wookey, whose bones are housed in nearby Wells Museum.
Circus man Mr Cottle, who bought the complex earlier this year for £6.5m, is going through a legal battle to have the 1000-year-old skeleton returned to the caves.