Iran is pressing ahead with major underground construction at a little-known mountain site, raising fresh alarms just months after U.S. and Israeli forces devastated its main nuclear facilities. Satellite images reviewed by the Washington Post, alongside independent analysis, show accelerated activity at Kuh-e Kolang Gaz La—known as Pickaxe Mountain—suggesting Tehran has not abandoned its suspected nuclear ambitions and may be cautiously rebuilding.

Engineers first began tunneling into the Zagros mountains in 2020, roughly a mile south of the Natanz complex, which U.S. warplanes struck with earth-penetrating bombs on June 22. While Iran has described the project as a centrifuge production plant to replace one lost to sabotage, analysts say the dimensions and depth of the facility—an estimated 260 to 330 feet underground, even deeper than Fordow—suggest it could serve more secretive purposes, such as uranium enrichment or the storage of near-weapons grade material.

The purpose remains unclear. International inspectors have never been allowed inside, and IAEA director Rafael Mariano Grossi has said his questions about the site were rebuffed earlier this year. U.S. officials, speaking anonymously, confirmed that intelligence agencies are monitoring the facility, though the CIA declined public comment.

Satellite imagery shows significant changes since the U.S.-Israeli bombing campaign: new perimeter walls, reinforced tunnel entrances, and expanding spoil piles from excavation. Heavy equipment, dump trucks, and trailers are now clustered around both eastern and western entrances, underscoring the ongoing tunneling work. Experts say efforts to bury the tunnels under dirt and rock point to attempts to harden the site against future airstrikes.

The activity comes as Iran continues to withhold full cooperation from international inspectors. The IAEA struck a deal with Tehran on September 9 that was supposed to allow access to all nuclear sites, but Iranian officials have since cast doubt on the agreement. President Masoud Pezeshkian has warned that rebuilding nuclear sites would only invite more U.S. strikes, while hard-liners have attacked him for weakness. Supreme Leader Ayatollah Ali Khamenei retains ultimate authority over the nuclear program.

Meanwhile, the fate of Iran’s most concerning nuclear material—nearly 900 pounds of uranium enriched to 60 percent purity before the June strikes—remains unclear. U.S. intelligence believes much of it may be buried under the rubble at Isfahan and Fordow. Without clear accounting, analysts warn, Tehran could still attempt to covertly fashion a nuclear device if it decided to move forward.

Israel and the United States unleashed the most devastating strikes on Iran’s nuclear infrastructure in 15 years, destroying nearly all of its centrifuges at Fordow, Natanz, and Isfahan. President Trump declared the program “totally obliterated,” but subsequent intelligence reports have been less definitive. Analysts say Tehran may now be trading speed for secrecy, focusing on hardened sites like Pickaxe Mountain to shield any future nuclear activity from outside attack.

Analysts note that Iran has also begun rebuilding missile production plants targeted during the June war.

While Tehran’s path back to nuclear weapons capability has been badly disrupted, experts warn it retains the capacity to reconstitute its program quickly if it makes the decision to do so.

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