From the BBC News:
The dungeon believed to have housed Robin Hood when he was caught by the Sheriff of Nottingham is to be surveyed using a laser.
It is part of a major project to explore every cave in Nottingham.
Robin Hood is believed to have been held captive in an oubliette (underground dungeon) located at what is now the Galleries of Justice.
The Nottingham Caves Survey is being conducted by archaeologists based at the University of Nottingham.