The Thames tunnel, sunken brainchild of architectural father and son mega-team the Brunels, was not only the worlds first underwater tunnel, but following delays in construction and an interrupted revenue stream, its first subterranean market place and finally circus. Victorian London was a far cry from the capital we see today, as horse-drawn carriages tore up the cobbled streets either side of the thames - the swirling cesspit which flowed through the city centre and out to sea - was manned by a series of small boats. But when it came to the titans of trade and industry, these small boats and the neighbouring Tower Bridge simply couldn't cope with the sheer amount of goods which needed to be transported from one side of the river to the other.

Enter the Brunels- Marc Isambard and Isambard Kingdom (yup thats Isambard Kingdom...) who worked tirelessly using their newly invented tunneling shield to construct a shaft 396m in length, 23m below the river Thames' busy surface. Now construction wasn't without its problems; floods, gas leaks and inevitable delays blighted the project and saw it commuted down from a trade route, to a footpath and eventually a circus. No doubt to the relief of the tunnel's investors, it was purchased in 1865 by the East London Railway Company. The tunnel's generous headroom, resulting from the architects' original intention of accommodating horse-drawn carriages, provided a sufficient loading guage for trains as well.

The conversion is not to take away from the project's magnitude- the construction of the Thames Tunnel showed that it was indeed possible to build underwater tunnels which was in itself a revolutionary concept. These days the tunnels can be viewed from Rotherithe and Wapping tube or as part of a walking tour offered by the Brunel museum, which incidentally I couldn't recommend more highly.