23,5cm x 17,5cm
Engraved on stainless steel 18/10 and framed.
The bridge was completed in 1894. It is about 240 metres (800 feet) in length and provides an opening 76 metres (250 feet) wide. Its twin towers rise 61 metres (200 feet) above the Thames. Between the towers stretch a pair of glass-covered walkways that are popular among tourists. The walkways were originally designed to allow pedestrians to cross even while the bridge was raised, but they became hangouts for prostitutes and thieves and so were closed from 1909 to 1982. The Tower Bridge was operated by hydraulic pumps driven by steam until 1976, when electric motors were put into operation; the steam power system is still kept (in good repair) as a tourist display. Because of the reduction in shipping at the London Docklands, however, the leaves are now seldom raised.