Chester Castle occupies a knoll overlooking the river at the south end of the walled city. Before the defenses were extended it stood outside their circuit. William the Conqueror founded the castle after the city had fallen, but he soon made Hugh d'Avranches Earl of Chester and granted the castle to him. The tower's upper floor contains a vaulted chapel in Norman Traditional style, adorned with the remains of newly-discovered frescoes. A length of inner curtain also survives.