King George III bought this Palace from the Duke of Buckingham in 1762. It was a gift for his wife Charlotte. It's been the official royal residence since Queen Victoria moved in but now Queen Elizabeth II has made the move to reside at Windsor Castle permanently. Of course she still uses Buckingham Palace to entertain state visitors and for her weekly meetings with the Prime Minister. Public access is very limited at the palace; people tend to look on from the gates, watching events like that changing of the guard. You can't go inside unless you happen to visit in August and September. Every summer a limited number of tickets are made available for tours of the state rooms.
Trafalgar Square is the heart of London. Its name commemorates the British naval victory at The Battle of Trafalgar in 1805. The square plays host to Nelson's Column, situated in the centre. It is surrounded by fountains that are topped with four large brass lions that are said to have been constructed from cannons taken from the French ships captured at Trafalgar. On top of the column is the statue of Admiral Lord Nelson, the commander of the British naval fleet at the time, who died as the Battle ended. The Square has some of the finest buildings in London, including the National Gallery and Admirality Arch. It's also infamous for it's rowdy population of pigeons.
Big Ben and The Houses of Parliament
The Palace of Westminster AKA The Houses of Parliament used to be the offical Royal Residence until the 1600's. Nowadays, the houses serve not as a royal palace, but as a place that holds the debating chambers of politicians, in both the house of lords and the house of commons. The palace contains over 1,000 rooms, but the house of lords and the house of commons are the most important. Apart from these chambers, the building also consists of libraries, committee rooms, dining rooms, and even bars and gymnasiums. The houses of parliament have at numerous times in the past been a target for terrorists, but the most famous historical attack came from Guy Fawkes and a group of Roman Catholic extremists, who attempted to blow the houses up in the Gunpowder Plot of 1605. Visitors can queue to watch Parliament in session from the public gallery and there are tours of the building available via booking.