The Tower Bridge is a distinctive attraction that matches the Tower of London in terms of aesthetics. Built in 1894, the bridge measures roughly 240 meters (800 feet) in length and has a 76-meter-wide aperture. Its twin towers soar to a height of 61 meters (200 feet) above the River Thames. A pair of glass-covered walkways run between the towers and are popular with tourists. It is an engineering wonder, consisting of massive mobile highways that rise up to allow ships to pass. The Tower Bridge was powered by steam-driven hydraulic pumps until 1976 when electric motors were installed.