The Institute for Science & International Security (the “good ISIS”) claims that high-resolution satellite imagery of Iran’s largest and most important remaining nuclear site reveals a recent scramble to defend it against a possible American or Israeli aerial strike.
According to satellite data from February 10, Tehran has improved the facility’s defense by taking advantage of any delays in such an attack since the demonstrations began on December 28.
The facility in question is a massive tunnel complex located at Kolang-Gaz La Mountain, also known as Pickaxe Mountain. This mountain is close to the nuclear facilities in Natanz, which, up until the June 2025 Israel-Iran War, served as the focal point of the Islamic Republic’s nuclear program.
For reasons that have not yet been completely explained, this facility was not hit by the June 2025 destruction of the majority of the other Natanz facilities, including the centrifuges that were in place at the time.
By 2021, construction had begun on the location, and in early 2022, the Jerusalem Post and the good ISIS think tank made the public aware of its presence.
The think tank claims that although the massive underground facility is relatively new and is still not believed to be operational, which is one of the reasons it may not have been hit earlier, there are worries that if it is not addressed, it may eventually be used to enrich uranium or even for a covert race to develop a small nuclear weapon.
It has undoubtedly drawn more attention and emphasis from Iran since June 2025 as its most significant intact facility for possible use in its nuclear program.
In order to make it even more impregnable, Iran has been excavating and constructing this new facility close to the Natanz area since the beginning. It would go well beneath the mountain there, which is much larger than the mountain atop the Fordow site, which the US bombed with bunker busters in June 2025.
According to him, the main mountain that houses the new Natanz tunnel complex is 1608 meters above sea level.
By contrast, Kūh-e Dāgh Ghū’ī, the mountain that housed the Fordow centrifuge enrichment plant, was roughly 960 meters high.
According to the think tank, this raises the Natanz mountain by roughly 650 meters, or more than 50%, so that any buildings constructed underneath it might be significantly more protected.
The president of the research tank, David Albright, stated in a prior report that “Fordow is already seen as so deeply buried that it would be impossible to destroy via aircraft attack.” It might be more difficult to demolish the new Natanz facility.
There are “continuing measures to harden and defensively enhance two of the tunnel entrances into the facility,” according to the most recent think tank assessment. Throughout the complex, imagery depicts continuous activity associated with this endeavor, including the movement of many vehicles, such as cement mixers, dump trucks, and other heavy machinery like truck-mounted cranes and backhoes.
The Western tunnel entrance extension is currently undergoing concrete pouring as of February 10. Soil and rock have been leveled and pushed back on top of the tunnel portal at one of the eastern tunnel entrances. They also installed a concrete-reinforced headwork for the tunnel entrance extension throughout the past month. According to the paper, “this permits more overburden in the form of extra rock, dirt, or concrete.”
“These efforts fortify the tunnel gates and provide additional protection against an airstrike,” the paper added. There are heaps of building supplies on the ground next to the eastern tunnel openings.
“The continuous presence of heavy construction machinery and materials around the site indicate that the facility is likely not yet ready for operations,” the report went on to say.
Furthermore, according to the report, “Iran has previously linked the construction to the reconstruction of a sophisticated centrifuge assembly plant, but the facility’s size and the tall mountain’s protection raised immediate concerns about whether other sensitive activities, like uranium enrichment, are planned. It appears unlikely that the visible utility support levels currently in place—one likely ventilation shaft with above- and below-ground power lines—will be enough to sustain such operations inside the tunnel.
Israel can therefore anticipate that the plant will not be able to do all of the nuclear activities that Iran lost when its primary sites in Isfahan, Fordow, and Natanz suffered significant damage in June 2025.
The last two months of work on the facility’s potential vulnerabilities, however, have merely made an already very challenging target even more challenging to hit if Tehran intends to increase its capabilities.
