Guildford Castle was probably founded by William the Conqueror soon after 1066. Later, a stone tower or keep was built, possibly by King Stephen in 1130-1150. The Tower was used in the 14C as a place of meetings and trials and as a prison and in the 16C it was used as a house with brick fireplaces being added. It was abandonedin the early 17C and fell into disrepair. In 2003-4 major conservatio work was undertaken and the Great Tower was re-opened to the public. New floors have been installed and a new roof which has made the building more accessible to visitors. The Tower contains a model of the original castle, circa 1300 and interpretation panels trace its history to the present day. There is a visitor platform on the roof which offers panoramic views of Guildford town and along the River Wey to St Catherine's.