The oldest intact building in London is generally believed to be the White Tower, which stands in the heart of the Tower of London.

Construction on the White Tower (which stands to the right in the picture) was started on the orders of William the Conqueror some time prior to 1070 and was completed by 1100. The newly appointed Bishop of Rochester, Gundulf, was placed in charge of the project which used stone imported from Normandy (much of this was replaced in later centuries).

Built as a towering stronghold and fortress for the English kings, the walls of the tower at 15 feet (4.5 metres) thick and 90 feet (27 metres) high. It was later enclosed by a curtain wall and moat, taking the shape of the Tower of London as we now know it by about 1350.

The White Tower, also known as the Great Tower, has been the scene of many dramatic events in British history – from the deposition of Richard II in 1399 to the disappearance (and possible murder) or the Princes in the Tower – Edward V and his brother Richard, Duke of York, around 1483 (two skeletons, which some believed to be theirs, were unearthed here in 1674).

The White Tower, which is now part of a World Heritage Site, contains the splendid 11th century Chapel of St John the Evangelist. While three of the turrets at the corners of the tower are square, the fourth – the north-east turret, is round and once contained the first royal observatory.

The onion-shaped domes and weathervanes on the turrets were added in the 1520s.

These days the tower contains an exhibition of royal armour – including that worn by King Henry VIII – as well as exhibits on the tower’s history.

WHERE: Tower of London (nearest tube station is Tower Hill); WHEN: Tuesday to Saturday 9am to 4.30pm; Sunday to Monday 10pm to 4.30pm (closing times are 5.30pm between March and October); COST £18.70 an adult/£15.95 concessions/£10.45 a child (children under five free)/£51.70 for a family of two adults and up to six children; WEBSITE: www.hrp.org.uk/TowerOfLondon/

PICTURE: Stephen Pond/Historic Royal Palaces