Cadbury Castle, formerly known as Camalet, is a Bronze and Iron Age hillfort and has been associated with King Arthur's legendary court at "Camelot". It is a scheduled monument.
Some have claimed to see and hear the ghosts of King Arthur and his men riding out from the hill. Some folklore states that this only happens every seven years.
For further information, please read Haunted Britain by Antony D. Hippisley Coxe.