It was begun by William I around 1066 and built deliberately just outside the City boundary to warn potential troublemakers. It was then extended by a number of monarchs until Edward I, and has been a palace, prison, menagerie, place of execution and stronghold for the crown jewels.
Famous occupants have included Sir Francis Drake, Anne Boleyn (executed by sword), Sir Walter Raleigh and Rudolph Hess during the second world war.
The tower is protected by forty Yeoman Warders (Beefeaters) and eight flightless ravens, whose departure, legend claims, would indicate the downfall of England. The Beefeaters live on site and their dogs and cats are buried in a pet cemetery within the moat of the Tower.
The small “exits” at the bottom of the tower are medieval drainage outlets.
There is an admission charge and often a long queue to visit the Tower. But you can see parts of it for free at night by getting tickets in advance to the ancient Ceremony of the Keys.