Horseshoe Bastion, which is located on the north eastern side of the Castle and forms part of the outer defences, was constructed between 1794 and 1805 as part of a vast programme of works to remodel the Castles defences and is one of four new bastions constructed in this period. The bastion was provided with a long covered access tunnel that extends beneath the ramparts and allows access from within the castle. (location accurate to the nearest 1m based on available information)