10 Downing Street
Number 10 Downing Street is well-known and famed for being the home of Great Britain's Prime Minister (currently David Cameron), but it actually used to be two separate houses. In 1682 Sir George Downing, the British Ambassador to the Hague, bought the piece of land we now know as 'Downing Street', and began to build upon it. However, people weren't too impressed with his apparently shoddy building work, and so Sir Downing earned himself a bit of a reputation as a bit of an unreliable rouge.
Before it became the official house of the Prime Minister, it was privately occupied by a man named Mr. Chicken, who moved out in 1732. It was then that King George II offered both houses as a gift to Sir Robert Walpole, who is considered to have first held the office of 'Prime Minister'.
These days, 10 Downing Street is one of the most heavily protected building in the UK. It is impossible to open the door from the outside as there is no handle (for obvious reasons), and even if you do manage to get inside, you still have to pass through a scanner, security gates and armed guards!
Believe it or not, there is an official 'Mouse Catcher' at 10 Downing Street. His name is Larry, and he is a cat from Battersea Dogs & Cats Home - the first cat (or any animal) to receive the official title.