The head of the International Atomic Energy Agency said that as a result of Israeli and U.S. strikes, the agency has “seen extensive damage at several nuclear sites in Iran,” including those three. Israel claims it has set back Iran’s nuclear program by “many years.”

Fordo, one of Iran’s most fortified nuclear sites, is known for producing highly enriched uranium, including weapons-grade material. Buried deep beneath a mountain, it was considered nearly impenetrable—until now. On June 22, the United States dropped 12 30,000-pound bunker-busting bombs on the site.