Despite its venerable, nay, medieval, appearance, this is a Victorian youngster. Constructed of steel, then clothed in Portland stone, it was deliberately styled in the Gothic persuasion to complement the Tower next door, and it's famous for its enormous bascules -- the "arms," which open to allow large ships through. Nowadays this rarely happens, but when river traffic was dense, the bascules were raised about five times a day.

The exhibition, Tower Bridge Experience, is a fun tour inside the building to discover how one of the world's most famous bridges actually works, and to see the fantastic views on the outside. First, take in the romance of the panoramas from the east and west walkways between those grand turrets. On the east, the modern super structures and ships of Docklands, and west, the best look at the steel and glass "futuristic mushroom" that is Greater London Assembly's City Hall, the Tower of London, St. Paul's, and the Monument. Then back down to the nitty gritty of the inner workings, which you learn about through hands-on displays and films. COST: £4:50; joint ticket available for the Monument. Tube: Tower Hill.