Tehran – A new report from the Institute for Science and International Security (ISIS) reveals Iran has ramped up construction at the secretive “Hammer Mountain” facility, located one kilometer south of the Natanz enrichment complex. Satellite images from June to September 2025 show heavy machinery, a new security wall, and at least five underground entrances—two eastern, two western, and one southern—some active, others concealed with soil and gravel. Since U.S. and Israeli airstrikes in June 2025 damaged Natanz, Fordow, and Isfahan, Iran has accelerated efforts to rebuild its nuclear program, evading IAEA inspections.

Experts assess Hammer Mountain, under construction since 2020, could serve as a centrifuge production plant to replace Natanz’s destroyed capacity, a nuclear metalwork site from Isfahan, or a new enrichment facility for higher-grade uranium. The site’s mountain burial, up to 90 meters deep, is designed to withstand bunker-busters like the U.S. GBU-57 Massive Ordnance Penetrator used in Operation Midnight Hammer. IAEA Director General Rafael Grossi has decried Iran’s lack of cooperation, with enriched uranium stocks exceeding JCPOA limits by 20 times.