Construction cranes stipple the skyline of Iran's capital. A city of 10 million, Tehran has been in a building boom for years.

But in the northeast corner of this sprawling, smoggy metropolis, something was torn down a few months ago, something behind a 20-foot concrete wall.

"It was a municipal sports complex," said a grizzled man who came to the door of the guard house, shrugging and sliding into a camouflage fatigue coat without losing the ash from the cigarette clenched in his lips.

"It wasn't big enough," he said, declining to be identified. "So they demolished it, and they want to rebuild it bigger."

The yellow sign posted at the front gate -- clean and new, in contrast to the graffiti-scarred walls -- told the same story: "Sport Cultural Complex of Kowsar."

But in a few days inspectors from the International Atomic Energy Agency will ask to see for themselves. The now-vacant acres facing Shian 7th Alley have raised suspicions that Iran may be building nuclear weapons. Iran insists it harbors no secret weapons program, but fellow members of the IAEA board issued a resolution Friday condemning the country for failing to cooperate with an inquiry into its activities.

Satellite images of the site show that between August 2003 and March at least a half-dozen buildings were pulled down. The IAEA is investigating the images, which suggested to U.S. government analysts that Iran was concealing nuclear activities. Iranian officials have denied that claim and said inspectors are welcome to survey the site.

According to the Institute for Science and International Security, an organization based in Washington that monitors nuclear proliferation, a layer of topsoil was also carted away from the area. A machine that detects radiation, called a whole body counter, was then brought to the site, according to the institute.

"The whole body counter itself is not a clear indication of a nuclear weapons program," said David Albright, president of the institute.

But the site was not included in a list of atomic research facilities Iran was obliged to provide last year to the IAEA, the U.N. nuclear watchdog, he noted. And by the time inspectors arrive, all they may be able to confirm is a vague sense of unease.

"It'll be hard to do sample work at that site," Albright said. "People will try. But these are the changes you make if you want to defeat the environmental sampling techniques of the IAEA."

Iran has pledged to continue working with the inspectors, who expect be in Iran at least through the summer. But the theocratic government appeared to be still absorbing the impact of the slap by the IAEA -- its second since March for Iran's lack of candor.

On Saturday, the state-run Tehran Times newspaper carried 10 articles on its first two pages about the nuclear issue. But at a news conference, Iran's official on the issue, Hassan Rowhani, declared that the IAEA resolution "does not have much significance."

Rowhani, secretary of the Supreme National Security Council, said Iran had not yet decided whether it would resume enriching uranium -- a process that produces fuel for energy or for weapons. Iran agreed last year to suspend enrichment activities after it acknowledged a nuclear program it had kept secret for 18 years.

European diplomats who insist that Iran's cooperation has been erratic have said they want Iran to give up enriching uranium permanently and back away from plans for a heavy water reactor, which could produce plutonium for a bomb.

Rowhani pledged to continue talks with France, Germany and Britain, the European countries that coaxed Iran last year to cooperate with the IAEA, but he also implied that the resolution would have unwelcome consequences.

"Since the Europeans have not met their commitment, we may take new decisions and announce them in the coming days," Rowhani said.

Satellite photos show the site facing Shian 7th Alley before and after several buildings were demolished.