Britain's Houses of Parliament also called Westminster Palace, in the London borough of Westminster, is the seat of the legislative body of the United Kingdom of Great Britain and Northern Ireland. A royal palace said to have existed at Westminster under Canute the Great, Danish king of England (1016-35) originally occupied the site of the present Houses of Parliament. The building, however, was built by Edward the Confessor (died 1066) and enlarged by William I the Conqueror. In 1512 the palace suffered greatly from fire and thereafter ceased to be used as a royal residence. St. Stephen's Chapel, traditionally founded by King Stephen, was used from 1547 for the meetings of the House of Commons, held previously in the chapter house of Westminster Abbey; the Lords used another apartment of the palace. A fire in 1834 destroyed the whole palace except the historic Westminster Hall and St. Stephen's Chapel.

Sir Charles Barry, assisted by Augustus Pugin, designed the present buildings in the Gothic Revival style. Construction was begun in 1840 and finished in 1867. The Commons Chamber was burned out in an air raid during World War II but was restored and reopened in 1950.

The House of Lords is an ornate chamber 97 feet (29.5 meters) in length; that of the Commons, a much plainer affair, is 70 ft long. The most famous features of the Houses of Parliament are the towers at each end of the vast complex. At the southwestern end is the 336-foot-high Victoria Tower, reputedly the largest square tower in the world. Whenever Parliament is in session, a Union Jack flies from its summit during the day. The tower at the other end is Big Ben, or more properly, St. Stephen's Tower-Big Ben is actually the nickname of the tower's 13-ton bell upon which the hours are struck. It was named for Sir Benjamin Hall, Commissioner of Works when the bell was installed. A light shines from the topmost point of the tower during night sessions of Parliament.