Capital Gate (The Leaning Tower of Abu Dhabi)

Capital Gate is a 160-metre, 35-storey tower beside the Abu Dhabi National Exhibition Centre, and holds the Guinness World Record as the world's furthest leaning man-made tower. It inclines 18 degrees westward — more than four times the tilt of the Leaning Tower of Pisa, whose lean is roughly 3.9 degrees and entirely accidental. Capital Gate's is designed.

The tower was designed by RMJM for the Abu Dhabi National Exhibitions Company (ADNEC), which also served as structural and services engineer on the project. Construction began in September 2007 and completed in 2011. The form is a shallow S-curve: near-vertical at the base, kinking about a quarter of the way up, then straightening again towards the top, with upper floors overhanging the ground-floor footprint by tens of metres.

Holding that overhang up required two unusual moves. The concrete core was pre-cambered — built leaning in the opposite direction to the final tilt, then post-tensioned on the side opposite the lean so it straightens as load accumulates. Outside, a steel diagrid exoskeleton of roughly 8,500 structural beams wraps the building, absorbing gravitational and wind forces; it was the first tower in Abu Dhabi to use the technique. Around 21,500 tonnes of steel went into the structure, and the foundations comprise a dense reinforced mesh above 490 piles drilled 20 to 30 metres down. An internal diagrid creates a tapered 60-metre atrium.

RMJM cited the wind-shaped forms of desert sand and the movement of the sea as the sources for the curve. Floors 18 to 33 house the Andaz Capital Gate hotel, operated by Hyatt, giving the building a publicly accessible interior; lower floors hold offices and conference facilities. The tower was the subject of a National Geographic Megastructures documentary.

Beside the Abu Dhabi National Exhibition Centre (ADNEC) on Al Khaleej Al Arabi Street, roughly ten minutes from Zayed International Airport on the road into the city. The lean is most legible from the ADNEC forecourt and the approach roads — stand well back on the north-eastern side to read the full overhang against the sky. For an interior view, the Andaz Capital Gate hotel occupies floors 18 to 33; the lobby and restaurants are open to non-residents.