Windsor Castle is the most famous of all castles in England. Still a principal home of the British royal family, the sprawling structure is the largest and oldest residential castle in the world. It has been the site of a royal residence for almost 1,000 years, since the time of William the Conqueror. Windsor’s strategic position, 20 miles west of London near the banks of the River Thames, made it an important fortress.

The most bloody episode in the history of Windsor Castle took place during the English Civil War, when Oliver Cromwell’s Roundhead troops seized the castle and used it as a fortress and the headquarters of the parliamentary New Model Army. The deposed monarch, Charles I, was briefly imprisoned at Windsor Castle and was buried here after his beheading in 1648.

Buckingham Palace is the official London residence of the British monarch. Located in the City of Westminster, the palace is a setting for state occasions and royal hospitality, and a major tourist attraction. It has been a rallying point for the British people at times of national rejoicing and crisis.

The Tower of London is a historic monument in central London, England, on the north bank of the River Thames. It is the oldest building used by the British government. The tower's primary function was a fortress, a royal palace, and a prison. It has also served as a place of execution and torture, an armoury, a treasury, a zoo, the Royal Mint, a public records office, an observatory, and since 1303, the home of the Crown Jewels of the United Kingdom.

It became the principal residence of the monarch in London in 1698, during the reign of William III and Mary II when Whitehall Palace was destroyed by fire, and became the administrative centre of the monarchy (a role it still retains). Mary I died there, with her heart and bowels being buried in the palace's Chapel Royal. Charles I slept rather less soundly -- as it was his final bed before his execution. Oliver Cromwell then took it over, and turned it into a barracks during the English Commonwealth period. It was then restored by Charles II.

Westminster Palace The Palace of Westminster, also known as the Houses of Parliament, is a complex of buildings in London. It is the seat of the two houses of the Parliament of the United Kingdom (the House of Lords and the House of Commons). The palace lies on the north bank of the River Thames in the London borough of the City of Westminster, close to the government buildings of Whitehall. The palace contains around 1,100 rooms, 100 staircases and 5 kilometres (3 mi) of corridors. Although the building mainly dates from the 19th century, remaining elements of the original historic buildings include Westminster Hall, used today for major public ceremonial events such as lyings in state, and the Jewel Tower.