Iran’s potentially most dangerous nuclear site is buried as deep as 100 meters under a granite mountain, according to new assessments, with one nonproliferation expert warning it must be "neutralized" before the U.S war with Iran ends.
This came as new figures released Wednesday by U.S. Central Command (CENTCOM) show that U.S. and Israeli forces launched Operation Epic Fury in late February, and have since struck more than 7,800 targets in Iran as the conflict enters Day 18.
"Before the United States and Israel end major combat operations against Iran, they must complete two urgent tasks," Andrea Stricker, deputy director of the Nonproliferation Program at the Foundation for Defense of Democracies, said in a policy briefing.
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"First, they must neutralize Pickaxe Mountain. Second, they must recover or eliminate highly enriched uranium stocks to prevent them from falling into the hands of surviving regime elements, other adversarial states or terrorist proxies."
High-resolution satellite imagery taken in mid-February shows Iran's accelerated efforts to reinforce the site at Kuh-e Kolang Gaz La — dubbed "Pickaxe Mountain" — against potential airstrikes, according to the Institute for Science and International Security.
"At one of the eastern tunnel entrances, rock and soil can be seen pushed back and leveled on top of the tunnel portal," the institute's report said.
"Additionally, over the last month, a concrete-reinforced headworks for the tunnel entrance extension was added. This allows for additional overburden in the form of rock, soil or concrete."
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The report added that "these efforts strengthen the tunnel portals and provide additional protection against an airstrike," noting visible piles of construction materials near the entrances.
Preventing Iran from having a nuclear weapon is one of President Donald Trump’s stated war aims.
In June 2025, U.S. forces already carried out strikes against nuclear facilities including Fordow, Natanz and Isfahan.
Iran had roughly 441 kilograms of uranium enriched to 60% as of June 2025 — enough material, if further enriched to weapons-grade levels, for multiple nuclear weapons, according to the International Atomic Energy Agency.
Rafael Grossi, its director general, also said March 9 that the U.N. watchdog believes roughly 200 kilograms of Iran’s highly enriched uranium stockpile are still stored in deep tunnels at a nuclear complex outside Isfahan.
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Grossi added that additional quantities of highly enriched uranium are believed to be at another nuclear center in Natanz, where Iran has constructed a new fortified underground facility at Pickaxe Mountain.
Meanwhile on March 9, Trump pointed to Iran’s efforts to resume nuclear activity at a deeper site and said Tehran has continued pursuing a nuclear weapon "even after we obliterated their key nuclear sites."
"They were starting work at another site, a different site … that was protected by granite … they wanted to go a lot deeper, and they started the process," Trump said, according to reports.
According to Stricker, the "different site" referenced by Trump is Pickaxe Mountain, where Iran has said it has been building a centrifuge assembly plant at the site since 2021. The site is a mile from its Natanz enrichment plant.
"The size of the facility, as well as the protection provided by the tall mountain, raised immediate concerns about whether additional sensitive activities are planned, such as uranium enrichment," The Institute for Science and International Security also noted in its report.
At the beginning of March, a vehicle was struck outside the site, presumably by Israel, the Wall Street Journal said, before suggesting that the vehicle strike was evidence the U.S. and Israel are watching the mountain carefully.
