This is one of the coolest bridges I have ever seen. Plans for the Tower Bridge were devised around 1876 when the east of London became crowded and a bridge across the Thames seemed necessary.
The bridge used to open almost 50 times a day but now it is only raised about 1,000 times a year. Bridge lifts are pre-scheduled (for cruise ships, etc) so check the bridge's website to find out times.
But the best view requires you to be on the bridge – see what I mean, looks like a fairy tale bridge!