Satellite Imagery Shows Surge in Construction at Iran's Pickaxe Mountain Days After Trump Strike Threat

A new analysis from the Center for Strategic and International Studies, released September 9, finds that Iran is pushing ahead with construction at a deeply buried facility known as Pickaxe Mountain. The work has picked up sharply this year, and it comes just days after President Donald Trump threatened to strike the site.

The CSIS team examined six years of satellite imagery. Their conclusion was blunt: there is more road activity at the site in 2026 than at any point in its history. They described a clear surge in construction.

The nature of the work has also changed. Iran appears to have moved past simply digging out the mountain. The imagery shows tunnel entrances being strengthened, internal roads paved, access areas reinforced and debris from the excavation cleared away. CSIS reads this as a shift from active excavation toward probable internal construction and further hardening of the exterior infrastructure.

Pickaxe Mountain sits roughly 2 km from the Natanz uranium-enrichment complex, dug deep into granite. Iran began developing it after a 2020 explosion damaged an above-ground centrifuge assembly building at Natanz, an incident widely attributed to suspected Israeli sabotage. Tehran then announced plans for a new underground centrifuge-related facility nearby, part of a broader move to put vulnerable nuclear infrastructure under mountains. Western and Israeli intelligence agencies have watched the site for years as a possible shelter for parts of the programme.

What the site is actually for remains unproven. Israeli intelligence has separately claimed that Iran may have moved centrifuges and components inside. CSIS says its analysis can neither substantiate nor refute that. In fact, the analysts point to several signs that the facility may not yet be ready for enrichment, if that is the intent: construction is still under way, there is no apparent increase in internal security, and there are no vehicles or equipment of the kind usually seen at an operational site. CSIS lists possible future uses including centrifuge assembly, enrichment, or other nuclear-related work such as uranium metal processing, but notes that no public evidence conclusively shows what Iran plans to run there.

Trump raised the stakes in July, warning that the US could hit the facility. "We'll be hitting that area pretty soon, and very heavily," he said. But CSIS says the site would be hard to destroy even with the GBU-57 Massive Ordnance Penetrator, the heaviest non-nuclear weapon in the US arsenal and one built for deeply buried targets. The depth and construction of the mountain raise doubts that it could reach the most important sections. A strike might still damage entrances and supporting infrastructure and disrupt activity, but damaging the surface is not the same as destroying what lies beneath.

Washington has met this problem before. During Operation Midnight Hammer in June 2025, American forces hit key parts of Iran's nuclear infrastructure, and while the damage was significant, deeply buried portions of some facilities proved much harder to eliminate. The Pentagon has since sought ways to extend its reach. CNN reported an emergency $1.2 million contract, issued shortly before the current US-Iran war, for work at a subterranean testing facility at White Sands Missile Range in New Mexico. Satellite imagery showed excavation there in February and March, and CNN's sources tied it to efforts to develop ways of targeting Iran's deepest facilities. The US Air Force is also pursuing a "next generation penetrator" to succeed the GBU-57, with prototype work begun in 2025.

The current surge follows months of earlier activity. Previous CSIS analysis found Iran accelerated work after the June 2025 strikes, then completed a security perimeter and reinforced several tunnel entrances. The latest imagery suggests the project is entering a more advanced phase. The International Atomic Energy Agency has asked for information about Pickaxe Mountain and requested access to the site. Whether that access is granted, and whether Trump's threat becomes a strike plan, are the questions to watch.