After William conquered England in 1066 AD, he needed a castle to live in when he was in London. He needed a castle that would protect London from invaders. But it had to also be a castle that would protect him, William, from angry English people. They didn’t like being conquered.
William built the White Tower in a Romanesque style, with rounded arches. Long narrow buttresses helped to support the heavy stone walls. Like the walls of Cairo just a little later, William’s walls have crenellations on the top. Crenellations are little walls that men could hide behind while they were shooting arrows at their attackers. (Most of the windows you see were added later).
Inside, the White Tower originally was only two stories high. You walked up and down on spiral staircases.
Built into the wall, William had several latrine toilets. They’re just a board with a hole in it, and a long chute down to the ground. William also had a well built into his castle. That way he could get water without going outside if someone attacked the castle.
A beefeater tells about the Tower of London
In the 1100s, King Richard built another stone wall around the White Tower, to be extra safe, and dug a moat. Later kings also worked on the Tower, and continued to live there sometimes until after 1500 AD.