Designed by Sir Horace Jones and opened in 1894, Tower Bridge is one of London's most recognizable landmarks. This famous monument is built on the River Thames and overlooks the iconic Tower of London. Due to the volume of river traffic in the 19th Century, the Tower Bridge was designed to have twin bascules that could be raised. One of the most fascinating features of the bridge is the Victorian-era engine room that houses the coal-powered motors used to raise the bridge lifts. The two towers, the North Tower and South Tower, are open to visitors. There is a glass-covered enclosed walkway that runs between the two that offers a bird's-eye view of vibrant city life. Guided tours are offered on a regular basis.