London is the capital city of both the United Kingdom and the constituent country of England. The ancient City of London to which the name originally belonged still retains its mediaeval boundaries, but the name “London” has long applied more generally to the whole metropolis which has grown up around it. An important settlement for around two millennia, London is today one of the world’s leading business, financial and cultural centres, and its influence in politics, education, entertainment, media, fashion and the arts all contribute to its status as one of the major global cities. London is the most populous city within city limits in the European Union with an official population of 7.5 million and has a metropolitan area population of between 12 and 14 million people. Its diverse population draws from a wide range of peoples, cultures and religions, speaking over 300 different languages. It is an international transport hub, with five international airports and a large port. It serves as the largest aviation hub in the world, and its main airport, the multi-terminal Heathrow, carries more international passengers than any other airport in the world. It also has the World’s largest underground railway system when measured by route length. London is a major tourist destination, with four world heritage sites and numerous iconic landmarks such as the Houses of Parliament, Tower Bridge, the Tower of London, Westminster Abbey, Buckingham Palace and the London Eye among its many attractions, along with famous institutions such as the British Museum and the National Gallery. Its main geographical feature is the River Thames which runs through the city from the south-west to the east. Windsor is a suburban town and tourist destination in the Royal Borough of Windsor and Maidenhead in Berkshire, England. It is best known as the site of Windsor Castle. Windsor Castle is the largest inhabited castle in the world and, dating back to the time of William the Conqueror, is the oldest in continuous occupation. The castle’s floor area is approximately 45,000 square metres. Together with Buckingham Palace in London and Holyrood Palace in Edinburgh, it is one of the principal official residences of the British monarch. Most of the kings and queens of England have had a direct influence on the construction and evolution of the castle, which has been their garrison fortress, home, official palace, and sometimes their prison. The castle’s history and that of the British monarchy are inextricably linked. Chronologically the history of the castle can be traced through the reigns of the monarchs who have occupied it. When the country has been at peace, the castle has been expanded by the additions of large and grand apartments; when the country has been at war, the castle has been more heavily fortified. This pattern has continued to the present day.