Despite its medieval, fairy-tale appearance, Britain's most iconic bridge was actually built at the tail end of the Victorian age, first opening to traffic in 1894. Constructed of steel, then clothed in Portland stone, the Horace Jones masterpiece was built in the Gothic style that was highly popular at the time (and it nicely complements the Tower of London, next door). The bridge is famous for its enormous bascules—the 1,200-ton "arms" that open to allow large ships to glide beneath. This still happens a few times per month (the website lists upcoming times), but when river traffic was dense, the bascules were raised about five times a day.
The Tower Bridge Exhibition is a family-friendly tour where you can discover how the bridge actually works before heading out onto the walkways for wonderful city views. First, take in the romance of the panoramas from the east and west walkways between those grand turrets. On the east are the modern superstructures of the Docklands, and
on the west is the Tower of London, St. Paul's, the Monument, and the misshapen steel-and-glass egg that is Greater London Assembly's City Hall (memorably described as "a glass testicle" by Ken Livingstone, mayor from 2000 to 2008). Then it's back down to explore the Victorian engine rooms and discover the inner workings, which you learn about through films and hands-on displays.