Before the strikes, Iran's primary enrichment site was at a facility in Natanz. The facility had been subject to sabotage and subterfuge by Israel for many years even before these attacks–including a that wrecked the centrifuges over a decade ago. Partially because it was such a target, Iran moved Natanz's centrifuges into an underground hall in recent years. Israel attacked the Natanz site on the first day of the war. It destroyed an enrichment facility on the surface known as the pilot fuel enrichment plant. Israeli war planes also struck power and other support facilities for the underground portion of the site. Israel also dropped bombs onto the buried centrifuge hall, although they did not appear to pierce the facility. On June 22, the U.S. followed up with a strike using two Massive Ordnance Penetrators to hit the underground centrifuge halls. "That facility was not so deeply buried and I would expect that the underground enrichment halls are also very severely damaged," says Jeffrey Lewis, a professor at the Middlebury Institute of International Studies at Monterey who has studied Iran's nuclear facilities for years. But Lewis also says that near Natanz, Iran has been digging out an enormous underground facility into the side of a mountain. That facility, whose purpose remains unclear, appears to be intact. Isfahan , Here’s what we know so far about the state of Iran’s nuclear program after the Israeli and U.S. attacks:, The U.S. joined that attack on Sunday, dropping 14 bunker-buster bombs on two sites. Iran retaliated with strikes on Israeli and American targets. Israel and Iran have since agreed to a ceasefire. Here’s what we know — and don’t know — about the state of Iran’s nuclear program..