What is Fordow? The nuclear site buried deep in an Iranian mountain, hit by president Trump’s bunker buster

However, Natanz had a key vulnerability—it was buried just eight meters (about 26 feet) below ground. According to the International Atomic Energy Agency, its surface buildings were completely destroyed in a previous Israeli attack. While the underground halls remained intact, the damage to its electrical systems suggested possible harm to the centrifuges, even before the US strike.

Fordow, however, was a different story. With about 3,000 centrifuges spread across two halls, it was much smaller, but buried 80 to 90 meters underground, inside solid rock. While Natanz enriched uranium to low levels (3–5%), Fordow was Iran's main site for higher-level enrichment—up to 60%, and traces of uranium enriched to 83.7% were recently detected there, a easy step from the 90% level required for nuclear weapons.

In essence, Fordow served as Iran's "insurance policy" for its nuclear program, a secure site where the regime could rapidly move to weapons-grade enrichment if it decided to build bombs.

Enrichment is the process of increasing the concentration of fissile material—a specific isotope, uranium-235—found only in small quantities in mined ore. High-speed centrifuges separate heavier particles from lighter ones, and the resulting gas is then converted back into metal. For weapons production, the fissile material is shaped into a sphere and combined with a triggering mechanism to form a nuclear bomb.

Satellite imagery underscores why Fordow posed such a major challenge to Israel and others concerned with Iran's nuclear ambitions. Winding roads lead directly into tunnels dug into the mountain, giving access to the underground centrifuge halls. Most of the facility—including thousands of centrifuges enriching uranium to near-weapons grade—were hidden deep within rock, shielded in a way that made it virtually invulnerable to standard aerial assaults.

A secret revealed

Originally a missile base run by the Islamic Revolutionary Guard Corps, Fordow's conversion into a nuclear enrichment site began around 2006–2007, according to Western intelligence. For years, its existence was kept secret until the US, U.K. and France exposed it in September 2009 after it was detected by intelligence services. Iran was forced to acknowledge the site to the International Atomic Energy Agency, claiming it was for civilian purposes.

But nuclear archive documents seized by Israel in 2018 told a different story: Fordow—referred to as "Project Al-Ghadir"—was planned as part of the "AMAD Project," Iran's covert nuclear weapons development program.