Shoulsbury Castle is perhaps the largest and best known of the defensive earthworks on Greater Exmoor. Early forms of it include Solsbury (Westcote 1630), Shorsbery (Risdon 1630), Salusbury (1815), Shoulsbury (1819), Showlsborough (Page 1890) and Shoulsbarrow (present OS maps). The root may therefore be the same as Solisbury above Bath, which seems to be named from the Roman-Celtic god Sulius Minerva to whom the Roman baths at Bath were dedicated. There is much to be said for calling it Shoulsbury (which conforms to local pronunciation) in preference to Shoulsbarrow which implies confusion with sepulchral mounds. Shoulsbury is situated on a south-western spur of the main western scarp of Exmoor, and water could have been obtained from tributaries of the river Bray which rises on the hill slopes within half a mile. The earthwork is bivallate (ie with two defensive ditches) excepting on the south where the steep scarp makes a second rampart unnecessary. Original entrances may have been in the middle of the west side of the inner rampart, and near its south east corner. It has already been observed that the sub-rectangular plan, the similarity of this plan with that of the known Roman fortlets at Martinhoe and Old Burrow (County Gate), and the slightness of the ramparts for a normal hill-fort, all cause some of us to wonder if it is Iron Age or Roman. The inner earthwork encloses about four acres and the outer earthwork about six in all. Within the north-east corner R.R.Clarke noted a circular mound about eleven yards in diameter which he conjectured might have been the base of a watchtower if it is not the remains of a round barrow. It has been said that two rapiers of c17th century date, 'no doubt lost in some minor skirmish of the Civil War', were found towards the end of the last century at Shoulsbury Castle.