The castle, after centuries of alterations, contains about 1,000 rooms and occupies 13 acres of land. William the Conqueror chose the site of Windsor Castle at 'New Windsor' - taking the name from the 'Old Windsor' which was used by the Saxon Kings of the Dark Ages. 'New Windsor' was 100 feet above the river Thames and on the edge of the Saxon hunting ground. Despite countless additions and alterations the outer walls and the central mound of the castle are still in the same position as those of the original castle built by William the Conqueror. It was a day's march from the Tower of London and intended to guard the western approaches to the capital of England.