No10 Downing Street

The front door is simply the most famous in the world.

Behind it lays a world of history and secrets, but the door can tell an interesting tale itself. For one thing, it has not always been black. During the early 20th century it was actually painted green. The original Number 10 door is a centrepiece of the Churchill museum in London. It was replaced with two identical doors that are swapped over whenever they need a spot of maintenance. The famous lion's head doorknocker and the brass letterbox date back to the 1770s. The letterbox is inscribed 'First Lord of the Treasury', the title held by every Prime Minister since Sir Robert Walpole. The '0' in the number 10 is painted at an angle as a nod to the original door, which had a badly-fixed zero, although some people think the '0' was painted at angle to replicate the Roman style.