Iran is reinforcing tunnel entrances at a mountain complex near its Natanz nuclear facility, according to analysis of new satellite imagery. The activity centers on Mount Kolang Gaz La, also known as Pickaxe Mountain, and comes amid ongoing, though stalled, negotiations with the United States over its nuclear program.
Images from February 10th, first analyzed by the Institute for Science and International Security (ISIS), show fresh concrete being laid at one of the tunnel entrances. A boom pump, used for delivering concrete, was observed at the location, according to analysts at ISIS and the UK-based intelligence analysis firm Maiar. At another entrance, rock and soil have been cleared and leveled. The construction suggests an effort to bolster the defenses of the underground complex.
The new security perimeter around the base of Mt. Kolang Gaz La was first observed in new commercial satellite imagery in April 2025, encircling the mountain peaks and connecting to the existing perimeter around the Natanz enrichment complex. The mountain contains a newly constructed, large tunnel complex, as well as a smaller one dating back to 2007, neither of which has been inspected by the International Atomic Energy Agency (IAEA).
The larger, newer complex, which may be completed this year or next, is intended to house an advanced centrifuge assembly facility, replacing one at the main Natanz site that was damaged in an explosion in 2020. The halls within this complex are more deeply buried than those at the Fordow uranium enrichment site, and the size of the complex raises concerns that it may also contain additional, undeclared nuclear capabilities, including a small gas centrifuge facility.
These developments follow a period of heightened tensions, including a 12-day war between Israel and Iran in June 2025. Then-President Donald Trump claimed that U.S. Strikes during that conflict “obliterated” Iran’s enrichment capacity, but also stated that Iranian officials were considering building a new site. Pickaxe Mountain was not targeted in those strikes, but the Natanz facility was hit.
Activity has also been detected at the nuclear complex in Isfahan, where entrances to tunnels appear to have been covered with earth, potentially to mitigate the impact of aerial attacks and hinder ground assaults.
Sina Azodi, Director of Program Studies at George Washington University, stated that Iran’s actions reflect an anticipation of potential future attacks. “Iran’s nuclear program hasn’t been destroyed. Once a country has the knowledge, capacity, and technology, everything can always be rebuilt,” he said.
The IAEA Director General, Rafael Grossi, has indicated that the possibility of a new nuclear agreement between Iran and the United States remains open, but that time is running short. As of February 13, 2026, no new negotiations have been publicly scheduled.