The Troll A oil platform has since been stripped of its title by the likes of Petronius and Berkot. It remains an impressive piece of structural engineering, standing at a height of 472 metres (1549ft) above the seabed and over 300 metres below the waterline.

The platform sits on four legs, each made from mathematically joined slip-formed conical cylinders that flare out smoothly to have a greater diameter at the top and bottom. The legs are built from steel-reinforced concrete, formed in one continuous pouring to allow them to withstand intense pressure from the ocean, and the structure’s 683,600-tonne weight (1.2 million tonnes with ballast). An elevator in the legs travels from the platform to the seafloor in nine minutes.

When construction was completed in 1996, the platform had to be towed over 200km from the Norwegian village of Vats to the Troll field, 80km north-west of Bergen. This was the biggest structure to ever be moved, in a process that took seven days and was televised as a major event throughout Norway.

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