London, the capital of the United Kingdom, was founded by the Romans around 43 AD as 'Londinium.' Over two millennia, it has grown from a small settlement on the River Thames into a global megacity. A unique political anomaly is the 'City of London'—often called the Square Mile—which is a tiny ceremonial county and the historic heart of the city. It has its own Lord Mayor, independent from the Mayor of London, and its own police force. London is famous for its iconic 'Beefeaters' at the Tower of London and the red double-decker buses. It was the first city in the world to build an underground railway, the London Underground (the Tube), which opened in 1863. The city serves as a global hub for finance, fashion, and the arts, and is home to four UNESCO World Heritage sites, including the Palace of Westminster and the Royal Botanic Gardens, Kew. Despite the Great Fire of 1662 and the Blitz of WWII, London has consistently reinvented itself while preserving landmarks like Big Ben and St. Paul's Cathedral.