The Castle of Exeter is not only a fortress of high antiquity, but is in many respects peculiar. It occupies the northern angle of the city, forming a part of its _enceinte_, and it crowns the summit of a natural knoll formed by an upburst of Plutonic rock, of a red colour, whence it derived its Norman appellation of Rougemont. The knoll rises steeply on the north-east and north-west from a deep valley, but on the other two sides the slope, though still considerable, is more gradual. The sides of the knoll have been scarped, and at the foot of its upper part a deep and broad ditch has been excavated, beyond which, to the north, a second scarp descends to the bottom of the valley. Towards the south, where the ground allowed of and required it, there was a second and outer ditch. The contents of the inner ditch were carried upwards and inwards to form a high bank round the original summit of the knoll, the central part of which was thus converted into a pit, and became the inner, and indeed the only, ward of the castle. In figure this ward, taken at the level of the circumscribing bank, is something between a square and a circle. Probably its outline was governed by the natural figure of the ground, and such angles as it now has are due to later modifications of the works. Originally then, the fortress was a hill camp, composed of a bank about 30 feet high, cresting the edge of the knoll, and outside scarped down about 60 to 80 feet deep to the bottom of a broad ditch, which again was reinforced on the less steep side by a second ditch. The main ditch towards the north-east and north-west has been filled up and converted into a broad public walk and garden, but the outer or second scarp still remains, and descends to the valley now occupied by the station of the London and South-Western Railway. Towards the south-east and south the ditch remains unaltered, and is a very fine example of an ancient earthwork. Towards the east it seems to have been filled up.