What are facts about the tower bridge in London?

Tower Bridge opened in 1894.
It is built of 11000 tons of steel, Cornish granite and Portland stone.
It is the only bridge across the river Thames which can be raised to allow tall ships to pass underneath.
When the bridge is raised, pedestrians can still cross to the other side of the river by using the walkway at the top of the bridge.
It is situated right next to the Tower of London - after which it is named.