New satellite images analyzed by the Institute for Science and International Security (ISIS) reveal that Iran has taken significant steps to fortify and restrict access to a secret underground complex at Mount Pickaxe, located just south of the Natanz nuclear facility. The images, provided by Airbus Defence and Space, show that by April 22, the two eastern tunnel entrances to the complex had been partially blocked with soil, a move that appears designed to hinder rapid vehicle access. On April 1, these entrances were still open and unobstructed, marking a swift and deliberate change in less than three weeks. The material used for the blockage does not fully conceal the tunnel openings, but it is sufficient to require heavy earthmoving equipment for clearance—a significant obstacle for any would-be intruders or inspectors.
The underground complex at Mount Pickaxe, also known as Kolang Gaz La, has long been a subject of international scrutiny. It is situated near Natanz, a site that has been the target of multiple Israeli airstrikes in recent years, most recently in June 2025, when centrifuges were reportedly “severely damaged if not destroyed altogether.” The complex’s tunnels are believed to be used for protecting valuable equipment or materials, possibly related to Iran’s nuclear program. Earlier this year, ISIS reported that old tunnel entrances had been buried and reinforced with concrete, suggesting that something of strategic importance may have been moved into the tunnels. The latest activity—blocking the eastern entrances—raises further questions about the nature of the operations inside.
Unlike similar tunnel complexes at Fordow and Isfahan, where entrances have been fully concealed, the partial blockage at Mount Pickaxe leaves the openings visible from above. This distinction may reflect a different purpose or a less urgent need for complete concealment. However, the use of soil to obstruct access is a clear indication of heightened security measures. “At this time, we do not yet see evidence of such blocking at the two western tunnel entrances,” ISIS noted in its analysis, adding that the activity “raises significant questions” about the complex’s function and the materials it may house.
Why This Matters: A Site of Strategic Concern
The Natanz facility is one of Iran’s most sensitive nuclear sites and its proximity to the underground complex at Mount Pickaxe underscores the strategic importance of the area. The recent blockage of tunnel entrances coincides with a period of heightened regional tensions, including ongoing talks between Iranian and U.S. Officials and a series of Israeli airstrikes targeting Iranian nuclear and missile infrastructure. The move to restrict access to the tunnels could be an effort to protect sensitive equipment, prevent unauthorized inspections, or prepare for potential future operations.
According to ISIS, the tunnels at Mount Pickaxe are buried deep underground, making them difficult to access without heavy machinery. The partial blockage of the eastern entrances suggests a deliberate effort to slow down or deter rapid entry or exit, possibly in anticipation of further developments. The Institute’s experts have previously noted that the complex’s design and location make it an ideal site for safeguarding nuclear-related materials or equipment, especially in the face of external threats.
Sequence of Events: From Open Access to Fortified Entrances
| Date | Observation | Analysis |
|---|---|---|
| April 1, 2024 | Eastern tunnel entrances open and unobstructed | No signs of fortification or soil blockage |
| April 22, 2024 | Partial blockage of eastern tunnel entrances with soil | Material used does not fully conceal openings but obstructs vehicle access |
| May 2, 2024 | Blockage confirmed; no evidence of similar activity at western entrances | Requires heavy equipment to clear; purpose and contents of tunnels remain unclear |
Stakeholders and Uncertainties
The fortification of the Mount Pickaxe complex affects multiple stakeholders. For Iran, the move may be a preemptive measure to secure its nuclear infrastructure amid escalating regional conflicts. For the international community, particularly the United Nations and its nuclear watchdog, the International Atomic Energy Agency (IAEA), the blockage raises concerns about transparency and access to critical sites. The IAEA has previously expressed concerns about Iran’s nuclear activities, and the latest developments could further complicate efforts to monitor compliance with international agreements.
What remains unclear is the exact nature of the materials or equipment stored in the tunnels. While some reports suggest the possibility of enriched uranium or other nuclear-related components, ISIS has not confirmed this. The Institute’s analysis focuses on the physical changes to the site, emphasizing the need for further investigation to determine the full extent of the activity inside the complex.
Next Steps: What to Watch For
The next critical checkpoint will be the release of further satellite imagery and independent analysis by nuclear experts. The IAEA is expected to continue monitoring Iran’s nuclear facilities, and any official statements from the agency could provide additional clarity. Developments in U.S.-Iran talks and the broader regional security landscape will be key indicators of whether the fortification of Mount Pickaxe is part of a larger strategic shift.
For now, the images and analysis from ISIS serve as a reminder of the complex and evolving nature of Iran’s nuclear program. The partial blockage of the eastern tunnel entrances is not just a physical change—it is a signal of the site’s growing importance and the lengths to which Iran may go to protect it.
What do you think about the latest developments at Mount Pickaxe? Share your insights and questions in the comments below, and share this story with others who follow nuclear security and international affairs.
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