This is both beautiful and the only draw-bridge on the river Thames. The bridge was built to fit in with the Tower of London (see separate entry), and so has a similar architectural style. If you a buy a ticket from the gift shop, which is located at the bottom of the tower that is on the righe in the picture below (which I didn't do) you get to see the machinery that operates the draw bridge, as well as go inside the towers.
If you stand on the bridge, you can feel the surface vibrate with traffic.