The first tunnel, the Thames Tunnel, which opened on March 25th 1843, was hailed as the "Eighth Wonder" of the world. It connected Rotherhithe with Wapping, and was built between 1825 and 1843 by Marc Brunel, father of the more famous Isambard.
The tunnel measures 35 feet (11 metres) wide by 20 feet (6 metres) high and is 1,300 feet (396 metres) long and runs at a depth of 75 feet (23 metres). Its excavation was extremely hazardous: the tunnel was prone to flooding, and six men died in 1828, it also exposed its workers to "foul air" which caused fevers. The work was then abandoned for seven years, until in 1834 Brunel succeeded in raising sufficient money to start work again. It cost a fortune to build and was never a financial success. Designed initially for use by horse-drawn carriages, lack of funds meant that it ended up as a foot tunnel only.
In 1865, it was bought by the East London Railway Company and was eventually absorbed into the London Underground (Tube) network and is today, after its re-modelling and reopening in 2010, as part of the East London line extension - and, bizarrely, an underground part of the new London Overground.
The Thames Tunnel is, however, one of at least 20 tunnels that run under the river today -more than in any other country or capital. There are 12 London Underground tunnels (9 in use, and 3 disused), three road tunnels, two foot tunnels (the Woolwich foot tunnel and the Greenwich foot tunnel), eight service tunnels, and two BT tunnels.