Spencer Tunick an American photographer, photographed 18,000 nude people in Mexico City's principal square (the Zocalo) on May 6 2007. This broke his previous record of 7,000 people in Barcelona Spain. The participants were in the nude as they posed in 4 different positions. Standing, saluting, lying down and crouching in a fetal position. Tunick has been arrested several times in the U.S. for obstructing traffic and alleged lewd conduct. Tunicks models do not receive any payment. Their only compensation is a signed photograph and the fun of being part of Tunick's art.