On 6 May 2007, 18,000 men and women gathered in Mexico City’s La Plaza de la Constitucion. At 6.50am, the crowd removed their clothes and a new world record was set. This was New York artist Spencer Tunick’s latest installation in his global project photographing nudes.

Thousands blushed as Tunick directed the crowd to bend over, lie down and crouch on the floor, capturing a wide array of daring poses. In this deeply religious city, the crowd let it all hang out, exactly as nature intended.

In this revealing documentary, Tunick’s ambitious project is laid bare. The artist encounters a host of testing problems that send the shoot into jeopardy, forcing him to climb surrounding buildings in a race to get the images he wants before dawn.