More than 18,000 people stripped down in Mexico City's main squaree, becoming part of American photographer Spencer Tunick's world's largest nude shoot.

"What a moment for the Mexican art scene!" Tunick said in a news conference. "I think all eyes are looking south from the United Sates to Mexico City to see how a country can be free and treat the naked body as art. Not as pornography or as a crime, but with happiness and caring."