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The Shard remains by far the largest building ever constructed in London, at around 310 metres. But it's not the tallest structure ever proposed for the capital. Here are six giants that would have reached even higher into the heavens above London.
1. Watkin's Tower (358 metres)
London almost got its own Eiffel-style tower. And, unlike the other entries on this list, Watkin's Tower became a partial reality. Sir Edward Watkin was one of those can-do Victorians with his fingers in many pies. Besides expanding the Metropolitan line and beginning his own version of a Channel Tunnel, Watkin also opened a pleasure ground at Wembley Park. As a centrepiece, he commissioned the world's tallest structure, an iron giant to rival — and surpass — the one in Paris.
Work began in 1892, and the structure climbed as far as 47 metres. For a variety of reasons (including marshy ground and financing woes) the tower was never completed, and was dismantled in 1904. It may have been a flop, but "Watkin's Folly" did leave a legacy. Wembley Stadium would eventually be constructed on the site — a location unlikely to have been chosen if Watkin had not built up his pleasure park and rail link.
2. Millennium Tower (386 metres)
In 1992, a Provisional IRA blast destroyed London's Baltic Exchange. Various schemes were put forward to replace the building, including this monster from Foster & Partners. It would have been London's tallest building by some 150 metres, and the sixth tallest in the world. The project fell foul of various campaigns, and never got started. The site was eventually occupied by 30 St Mary Axe, better known as The Gherkin, and also by Foster & Partners.
3. Green Bird (442 metres)
The so-called 'Green Bird' was designed in 1990 by Future Systems, most noted for the futuristic Media Centre at Lord's. The 'Green' epithet refers to its eco-friendly design, though we feel a more saucy nickname might have been found had this colossal dildo gone ahead. Renders from the time show it standing proud on the Battersea Power Station site.
4. Metropolitan Sepulchre (457 metres)
London's population skyrocketed in the 19th century which, by somber corollary, meant London's toll of deaths also ramped up. What to do with all the bodies? In 1829, architect Thomas Wilson came up with this, a vast pyramid of the dead on Primrose Hill. It was designed to stow some 5 million deceased Londoners, which would have caused some serious crowd-control issues come the blowing of Gabriel's trumpet. The London Dead has some excellent research on the structure.
5. Citygate Ecotower (485 metres)
Back in 2002, M3 Architects dreamed up this mighty sail of a building for Aldgate High Street. The mixed-use tower would have lived up to its eco name by incorporating natural ventilation, solar panels and wind turbines. As it happened, the scheme — more of a vision than a full proposal — enjoyed the lowest possible carbon footprint by never getting built.
6. Mile-high Eco Tower (1,500+ metres)
And then we have the tower so preposterously large that we considered changing the scale on our diagram to include it. The Mile-high Eco Tower never troubled the planning process, but was put forward in 2008 by Populararchitecture as something of a talking point. The concept imagines a whole city in one mile-high tower, with 100,000 people living and working across 500 floors. Housing crisis solved! Mock-ups of the tower show it in a variety of London locations, including a plot near Blackfriars and somewhere in the West End.