Like Lescudjack Castle (which was bigger) and Trencrom (smaller), Chun Castle is a hilltop fortress dating from about 500 BC. It has two stone walls and ditches encircle the summit of the hill. The entrances are staggered to make it harder for the enemy to enter. 'Chun' is a Cornish name derived from 'Chi Woen' or 'Building on the Downs'.