Folklore

Cadbury Camp (Nailsea)
Hillfort

It is believed that there is an invisible door in Cadbury Hill, Nailsea. ... whoever finds this door and enters will encounter the ghosts of King Arthur and his Knights of the Round Table.

The door recalls that at Alderley Edge. But I do hope it’s the real Arthur and his knights, and not just ghosts. From the 2007 ‘Haunted Somerset’ by John Garland.