Founded by William the Conqueror in 1066, enlarged and modified by successive sovereigns, the Tower is today one of the world's most famous and spectacular fortresses and a UNESCO World Heritage Site. Discover its 900-year history as a royal palace and fortress, prison and place of execution, mint, arsenal, menagerie and jewel house. In the winter you can skate on the dry moat. The Tower contains enough buildings and exhibits to keep a family busy for a full day, with plenty of both warlike and domestic contents. Some areas, such as the St John's Chapel in the White Tower, do not allow photography, but these are clearly signposted. Beefeaters, who are all retired sergeant majors from the British Army, provide guided tours for free as well as ceremonial security. See history come alive – go to the Ceremony of the Keys at the Tower of London. This ceremony, the locking up of the Tower, has been performed every night at 10PM for 800 years. Tickets for the ceremony are £5 and must be prebooked.