Troll A platform

Built from reinforced concrete, as of 2014[update], it was the tallest structure 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.

[5] The legs must be able to withstand intense pressures, so the walls of Troll A's legs are over 1 metre thick and are made of steel-reinforced concrete that was formed in one continuous pour – a lengthy process that takes 20 minutes per 5 cm laid.

Each leg is a mathematically joined composite of several conical cylinders that flares out smoothly to greater diameters at the top and bottom, so each support is somewhat wasp-waisted when viewed in profile and circular in any cross-section (see picture at right).

The legs use groups of six 40 metres (130 ft) tall vacuum-anchors holding them fixed in the mud of the sea floor.

[11] Gas rises from 40 wells and is exported through a number of pipes to a processing plant at Kollsnes.

[12] In 2006, the 10th anniversary of Statoil's operatorship of Troll gas production was celebrated with a concert by Katie Melua held at the base of one of the hollow legs of the platform.