Construction activity has accelerated at Iran’s Pickaxe Mountain underground complex near Natanz, with satellite analysis indicating a 2026 shift from excavation toward probable internal building work. IAEA director-general Rafael Grossi confirmed movement around the site, which inspectors have never entered and can assess only through remote imagery. The unfinished facility is buried 330 to 475 feet beneath a mountain and appears designed to house an enrichment plant beyond the reach of US bunker-busters, although no verified evidence shows nuclear material or active enrichment there. President Trump warned Iran over the activity at a GOP midterm convention and said the United States would respond forcefully if Tehran advanced the project. Trump had also said in July that the area would soon be hit, but no strike followed. Pickaxe Mountain was not targeted during the current war or the 12-Day War in June 2025. Iran began work on the complex after sabotage at an Iranian centrifuge assembly facility in 2020 and has maintained that its nuclear program is peaceful. CNN has reported indications that the United States is developing weapons intended to overcome the site’s granite shielding.