IAEA observes construction activity at Iran’s Pickaxe Mountain nuclear site

The UN’s nuclear watchdog has confirmed that construction is picking up at one of the most closely watched and least accessible sites in Iran’s nuclear program. Pickaxe Mountain, an underground complex located roughly 1.5 to 2 kilometers south of the Natanz uranium enrichment facility, is showing fresh signs of building activity, according to the International Atomic Energy Agency. IAEA Director General Rafael Grossi acknowledged the activity in a September 10, 2026, interview, while noting that inspectors have never set foot inside the facility. The agency has been limited to satellite imagery for its assessments. What we know about Pickaxe Mountain Construction at the site began in fall 2020, reportedly triggered by sabotage at Natanz’s above-ground enrichment facility. The complex features tunnel entrances designed to reach halls buried at least 100 meters beneath the mountain. Satellite analyses from independent organizations, including the Institute for Science and International Security and the Center for Strategic and International Studies, show a noticeable uptick in construction-related work throughout 2026. Paved roads, hardened entrances, and expanded access networks are...