U.S. President Donald Trump has repeatedly threatened to bomb an under-construction Iranian nuclear site buried deep beneath a mountain, as tensions escalate between the two nations. The facility, known as Kuh-e Kolang Gaz La, or 'Pickaxe Mountain,' is located on the southern side of Iran’s Natanz nuclear enrichment site.
Trump acknowledged the possibility that Iran may have moved centrifuges to the site, potentially at a depth that would challenge even the most powerful U.S. bombs. "We’ll be hitting that area... probably pretty soon. And there’s not a thing they can do about it," Trump told journalists. He previously warned that "Pickaxe is a possible target for a nice big fat shot right near the front door."
The new project at Pickaxe Mountain is being constructed adjacent to the Natanz facility, approximately 140 miles south of Tehran. Natanz, a complex of both above-ground and underground facilities, has been a focal point of international concern for two decades. Repeated sabotage attacks on Natanz, including one attributed to Israel that destroyed a centrifuge manufacturing site, prompted Iranian officials to begin constructing the Pickaxe Mountain facility.
Construction commenced in 2020, following an incident that Iranian authorities described as an explosion caused by sabotage at the Natanz site. At the time, Tehran claimed the sabotage caused significant damage, and Iran's then-nuclear chief, Ali Akbar Salehi, announced the start of construction for a "a modern, larger and more comprehensive hall in all dimensions in the heart of the mountain near Natanz" for producing advanced centrifuges. Centrifuges are used to rapidly spin uranium gas to enrich it.
Experts believe the scale of the project suggests Iran intends to use the underground facility for uranium enrichment and centrifuge construction. The facility, sprawling across approximately 1 square mile, is protected by anti-aircraft batteries, fencing, and Iran’s paramilitary Revolutionary Guard. Satellite imagery reveals multiple tunnel entrances.
Analysis from experts at the James Martin Center for Nonproliferation Studies has suggested that Iran is likely constructing the facility at a depth of between 80 and 100 meters (260 to 328 feet). Digging has continued since that assessment, with some experts indicating it could be even deeper. The U.S. has developed the GBU-57 bomb, capable of penetrating at least 60 meters (200 feet) of earth before detonation.
The Institute for Science and International Security in Washington suggested that potential targets could include above-ground power supply lines, ventilation shafts, and open tunnel entrances. Satellite imagery indicates the site features two pairs of entrances and a recently completed security wall. Following strikes from the U.S. and Israel, a pair of eastern tunnel entrances have been hardened and partially backfilled, though not completely sealed, according to the ISIS thinktank. Sam Lair, a fellow at the Foreign Policy Research Institute, noted that strengthening tunnel entrances could complicate targeting with penetrating munitions.
Trump's reference to striking the site "in the front door" suggests an attack might aim to seal the entrances rather than penetrate the underground caverns. U.S. officials have reportedly discussed using two GBU-57 bombs in succession to destroy such a facility, though it remains unclear if this would be effective against a site as deep as Pickaxe Mountain.
It remains unclear what materials are stored at Pickaxe Mountain, as the United Nations' nuclear watchdog has never gained access to the site. Following attacks during the 2025 war between Iran and Israel, Iran claimed that areas around its Bushehr nuclear power plant and the planned Darkhovin nuclear plant came under attack, though no damage to the Bushehr reactor was reported. The International Atomic Energy Agency stated there was no atomic material at the Darkhovin site during its last inspection.
In 2025, the U.S. conducted strikes on Iran’s nuclear sites at Fordo, Isfahan, and Natanz, all of which were engaged in uranium enrichment. Both the U.S. and Israel stated their objective was to prevent Iran from developing nuclear weapons. Iran has consistently maintained its nuclear program is for peaceful purposes, and the IAEA and Western intelligence agencies do not believe it has had an active military nuclear program since 2003. Israel is widely believed to be the only nuclear-armed state in the Middle East.
Iran's late Supreme Leader Ayatollah Ali Khamenei had previously issued a religious ruling against the development of nuclear weapons. However, his son and successor, Mojtaba Khamenei, has not publicly addressed the issue. Building a nuclear weapon would require Iran to enrich uranium to 90 percent purity, construct a bomb, and potentially miniaturize it for missile delivery—a process that experts estimate could take months or years and carry a high risk of detection.