Where is Fordow in Iran?: Fordow is an underground uranium enrichment facility built inside a mountain near Qom, approximately 180 km south of Tehran.
How deep underground is the Fordow facility?: Fordow is built approximately 100 metres inside a mountain, making it resistant to conventional bunker-busting munitions such as the GBU-31.Source: The War Zone / Army Recognition analysis
Was Fordow destroyed in the 2026 Iran strikes?: CENTCOM confirmed GBU-72 penetrators were used against Fordow. Whether the underground enrichment halls were destroyed has not been independently confirmed. The IAEA has no current inspector access.Source: CENTCOM
How many centrifuges does Fordow have?: Fordow houses approximately 2,700 centrifuges and was Iran's primary site for enrichment to 60% U-235 before IAEA inspectors were expelled.Source: IAEA
Can the GBU-57 destroy Fordow?: The GBU-57 Massive Ordnance Penetrator was the weapon designed to defeat Fordow. Defence analysts confirmed it was not used in the opening weeks of the 2026 campaign. The GBU-72 was confirmed used, but its effectiveness against Fordow's depth is not independently verified.Source: The War Zone / Army Recognition
What is the enrichment level at Fordow?: Fordow enriched uranium to 60% U-235 before IAEA access was cut. Iran's total 60%-enriched stockpile stood at 440.9 kg, enough for roughly seven weapons if further enriched to 90%.Source: IAEA
Why was Fordow built inside a mountain?: Fordow was deliberately sited underground to resist air strikes. Iran began constructing it covertly; the facility was disclosed to the IAEA in 2009 after Western intelligence detected it.
Is Fordow operational after the 2026 strikes?: Operational status is unknown. IAEA inspectors have no access. The IAEA Director General assessed that Iran's enrichment capacity and stockpile likely survive, even if surface infrastructure was damaged.Source: IAEA

Background

Fordow is Iran's most hardened nuclear facility and the one site US-Israeli strikes could not credibly destroy without the GBU-57 Massive Ordnance Penetrator. Built 100 metres inside a mountain near Qom, the facility was designed to survive conventional bunker-busters. Defence analysts confirmed that only GBU-31 2,000-lb munitions were used in the opening weeks of the 2026 campaign — weapons that penetrate just 1-2 metres of reinforced concrete, far short of Fordow's depth. CENTCOM later confirmed the GBU-72 Advanced 5K Penetrator was used against nuclear sites including Fordow.

Fordow houses around 2,700 centrifuges and was Iran's primary site for enrichment to 60% U-235 before inspectors were expelled. The IAEA has been denied access for over eight months. Iran holds 440.9 kg of 60%-enriched uranium across its facilities; if further enriched to weapons-grade 90%, that stockpile is sufficient for approximately seven nuclear devices. IAEA Director General Grossi assessed that military action cannot eliminate Iran's nuclear programme: the material and capacity remain even if surface infrastructure is damaged.

The IAEA disclosed in early March 2026 that Iran has a fourth enrichment site at Isfahan, whose operational status inspectors cannot determine. Fordow's survival matters beyond the physical: it is Iran's insurance against surface-level destruction elsewhere and the centrepiece of its deterrent posture.

How the World Sees Them

IAEA

Inspectors have had no access to Fordow for over eight months. The agency cannot verify stockpile movements or whether centrifuges remain operational.

Iran

Fordow is the proof that enrichment survives air power. Built specifically to resist attack, it anchors Tehran's claim that the nuclear programme is indestructible.

United States

CENTCOM used GBU-72 deep-penetration munitions against Fordow. Whether the underground enrichment halls were destroyed has not been independently verified.