The weight of the building is supported entirely by 12 stout outer columns, which form the square perimeter of the building, plus four inner columns at the corners of a smaller, inner square.

ECONOMIST: AN ENGINEERING MYSTERY

The Inner City covers an area of 2.99 square kilometres (1.15 square miles) and the outer walls surrounding the city east and west of the Euphrates enclose an area of 9.56 square kilometres (3.69 square miles).

UNESCO: OFFICE FOR IRAQ

He transformed the association's previously impenetrable inner sanctum, moving the entire operation from Lancaster Gate to new offices in Soho Square and overseeing a fall in the average age of staff from 55 to 32.

BBC: Profile: Adam Crozier