Troll-A

The Troll A platform is a condeep offshore natural gas platform in the Troll gas field off the west coast of Norway. It is the tallest construction that has ever been moved to another position, relative to the surface of the Earth, and is among the largest and most complex engineering projects in history. The platform was a televised sensation when it was towed into the North Sea in 1996, where it is now operated by Statoil. The Troll A platform has an overall height of 472 metres (1,549 ft), weighs 683,600 tonnes (1,2 million tonnes with ballast) and has the distinction of being the tallest structure ever moved by mankind. The platform stands on the sea floor 303 metres (994 feet) below the surface of the sea and one of the continuous-slip-formed concrete cylindrical legs (the leg containing the import and export risers) has an elevator that takes over nine minutes to travel from the platform above the waves to the sea floor.