Iran's two primary uranium enrichment sites tell a story of ambition driven underground. Natanz, first exposed by Iranian dissidents in 2002, became the country's primary enrichment hub, housing both the Fuel Enrichment Plant and the Pilot Fuel Enrichment Plant. Thousands of centrifuges spun inside its halls, processing uranium hexafluoride gas into increasingly enriched material. After the facility's existence became public, it drew the sustained attention of the IAEA and Western intelligence agencies. Fordow followed a similar pattern of secrecy followed by revelation. Converted from a military missile base into an enrichment facility, it was dug deep into rock specifically to resist aerial attack. Under the 2015 Joint Comprehensive Plan of Action, Iran agreed to cease enrichment at Fordow and convert it to a research center. Compliance did not last. By 2024, advanced IR-6 centrifuge cascades were operating inside the mountain once again.

On Iran's Persian Gulf coast, the Bushehr Nuclear Power Plant represents the program's most visible civilian face. Its origins stretch back to the Shah's era, when construction began with German assistance in the 1970s. Iraqi air strikes during the Iran-Iraq War in the mid-1980s damaged the partially built reactor. Construction resumed only in 1995, when Iran contracted with Russia's Atomstroyexport to install a 915-megawatt pressurized water reactor. Russia began delivering nuclear fuel in December 2007, and the reactor was completed in March 2009. Operational control transferred fully to Iran in September 2013. In 2014, Iran and Russia signed an agreement to build two additional reactors at the site, with construction formally starting in March 2017. Meanwhile, 300 kilometers inland, the Arak heavy water reactor raised different concerns. Its design closely resembled reactors used to produce weapons-grade plutonium, and assessors estimated it could yield enough material for up to two nuclear weapons annually.

The ancient city of Isfahan, renowned for its Safavid architecture, also hosts one of Iran's densest concentrations of nuclear infrastructure. The Isfahan Nuclear Technology Center, established in 1984 with Chinese assistance, employs 3,000 scientists and operates three research reactors. Alongside it sit a uranium conversion facility, a fuel manufacturing plant, a fuel element cladding plant, and a nuclear waste storage facility. Isfahan is suspected of being the primary location for Iran's weapon development work. In September 2008, IAEA experts reported they had only limited access to the site, and that a quantity of uranium sufficient for six nuclear weapons had been moved from Isfahan to undisclosed locations at a stage in the enrichment process that was not monitored. By June 2022, the IAEA reported that 90 percent of Iran's most highly enriched uranium had been relocated to Isfahan facilities housing equipment for converting uranium gas into uranium metal -- a step with direct weapons applications.

At the Parchin military complex southeast of Tehran, the question was never about enrichment but about weaponization. Iran presented Parchin as a conventional explosives testing site, but IAEA inspectors were searching for evidence of implosion testing consistent with nuclear weapon development. In November 2011, they identified a large explosive containment vessel inside the complex and reported credible information that weapons-related experiments had been conducted there. Iran denied access. Satellite imagery from 2012 showed a building draped in a pink tarpaulin and evidence of demolition and earth removal -- what investigators interpreted as efforts to eliminate incriminating evidence. In June 2016, despite Iran's continued denials, IAEA investigators found traces of uranium at Parchin, establishing the first physical evidence of nuclear activity at the military site.

In June 2025, the confrontation turned kinetic. The US Air Force struck Fordow with six B-2 Spirit bombers dropping twelve GBU-57A/B Massive Ordnance Penetrator bombs, weapons designed specifically to reach deeply buried targets. IAEA chief Rafael Grossi later confirmed that almost all sensitive equipment at the site had been destroyed. Israeli strikes targeted Natanz in the same month, destroying the above-ground enrichment facility. Yet Grossi added a sobering caveat: if Iran chose to further enrich its existing uranium stockpile to 90 percent, the process would take only a few weeks. The network's geography tells its own story. From the Saghand uranium mine in the central desert, operational since 2005, to the Tehran Research Reactor at the heart of the capital, Iran's nuclear infrastructure spans thousands of kilometers. Even after the 2025 strikes, satellite imagery showed Iran accelerating construction at a new underground site tunneled into the Zagros Mountains south of Natanz -- a mountain called Kuh-e Kolang Gaz La, or Pickaxe Mountain.