The massive guardroom that dominates the entrance at the top of the hill was built c 1407-13 by Henry IV, the son of John of Gaunt, Duke of Lancaster. Much of the rest of the medieval castle, notably the Great Keep and Hadrian's Tower, was incorporated into the numerous additions made in the late 18C. The remarkable neo-Gothic Shire Hall houses a remarkable sculpted stone ceiling and a collection of coats of arms.