Along the River Thames
London, like Paris, is a city that was built on a river, the River Thames. When the city was built nearly 2000 years ago, the river was an important part of the economy. In fact, it played an important role all throughout history. Today it is used more for leisure. At the Westminster bridge port there are a variety of cruise boats that will take you up the river and back to get a river view of the city. Although not as many tourist attractions lie along the river, there are quite a few and it is a tranquil break from walking of riding the Underground.
Along the River you will find Big Ben and the House of Parliament, St. Paul's Cathedral seen beyond the Millennium Bridge, and the Tower of London.

Other historic sights pop up along the way, like the Globe Theater and the London Tower Bridge. It is best to take a boat with a guided tour if you don't want to miss anything.