Spencer Tunick did his thing in Barcelona on Sunday. But Barcelona did more than Spencer's thing.

While Mayor of New York, Rudolph Giuliani censored Tunick's art, along with the inclination of New Yorkers to happily get naked in its service. Giuliani had managed to arrest, and sometimes jail, Tunick 5 times. Three years ago a photoshoot much smaller than Barcelona's was proposed for a Sunday dawn in an area virtually empty of people, but there was to be no joy, no art in Gotham that morning, thanks to our prosecutorial hypocrite.

In Barcelona the authorities seem to have had no problem with 7,000 (described as up to 12,000 elsewhere) happy naked Spaniards filling a "sweeping Barcelona boulevard" in daylight, and even provided a nearby massive convention hall for an assembly area.

But the Catalonian crowd was interested in more than art or mass urban nudity. As Tunick gave them the go-ahead, speaking into a microphone,

The crowd erupted into cheers and then chants of "No War!" and "No to Bush!"

Ozan Sezen, who works with computers, said he had read with dismay of Mr. Tunick's repeated installation-related arrests in New York City several years ago. The Supreme Court eventually ruled that Mr. Tunick had a right to stage his art outside without being jailed, but the Giuliani administration rejected his subsequent permit request; Mr. Tunick has not approached Mayor Michael R. Bloomberg for permission.

Mr. Sezen, 35, who was wearing a T-shirt that said "Rock Solid Beefcake," prepared to take it off.

"In many of his exhibitions, there are a lot of fat guys, which makes it much easier," he said.

The time came. There was loud cheering, and the sound of thousands of underpants hitting the floor. Everyone walked outside, naked.

Then it was over. Some people jogged nude up and down the boulevard. Others re-dressed. Inside, Scott Ansell, 31, an Englishman who had already taken part in an earlier work by Mr. Tunick, involving hundreds of naked people riding the escalators in a London department store, mused on the cultural differences.

"The English seemed a bit more giggly," he said. "I get the impression that half of the people here will be naked later today, anyway."

His friend Jane Hyde, 44, said of the apparent Spanish tendency to spank their own naked rear ends as a form of applause, "That bottom-smacking thing is rude!"

For a small slideshow of pictures, see Reuters.