Oliver's Battery is on a hill overlooking the island of St Mary's to the south-east.; It is triangular in shape, the sides of which are roughly 25 metres by 30 metres by 30 metres (82 ft by 98 ft by 98 ft) in length. The battery was entered from its north-western side, and in the north-east corner there was a small building, approximately 6 metres by 3.5 metres (20 ft by 11 ft), which may have been a store or a temporary gun magazine. The artillery pieces were located in the south-eastern corner of the battery, where a gun platform, in diameter, occupied the highest part of the fortification.
