This is one of the greatest mysteries surrounding Iran's nuclear program: the complex under Pickaxe Mountain, also known as Pickaxe. What is known about this site?
The mysterious underground complex next to Iran's nuclear facility in Natanz has attracted world attention after US President Donald Trump said the US could attack it because, according to him, it houses uranium enrichment centrifuges. Iran has already threatened to "expand" the war if the US attacks nuclear facilities again. Meanwhile, the US ambassador to the UN announced that for the second consecutive night, the attacks on Iran had been suspended to give diplomacy the necessary time.
Tehran has released almost no information about the complex, which is located under a nearby mountain, which in Farsi is called "Kuh-e Kolang Ghaz La" or Pickaxe Mountain. It is also known as the Pickaxe. Inspectors from the International Atomic Energy Agency (IAEA) have never been allowed to visit the site. Information about it comes only from satellite images and intelligence data. In recent years, it has appeared in reports on Iran's nuclear program, but it is not clear what it is used for. These ambiguities make it one of the most closely watched locations related to Iran's nuclear program.
What is known about this mountain?
The underground complex is located south of Tehran - in Isfahan province. It is carved into the mountain about two kilometers from the Natanz uranium enrichment facility - one of the most important for the country. Satellite images show that since 2020, construction has been underway there - tunnel entrances, roads, security systems and a large amount of stones brought out during the excavation.
It seems that after July 2020 (when a mysterious explosion damaged the Natanz facility), Iran has intensified construction activities around the Pickaxe Mountain. Authorities in Tehran declared it sabotage. A few months later, the Islamic Republic officially announced its plans to build a new underground facility, which would be in a safer location. Authorities announced that it would be bigger and better.
The American Institute for Science and International Security estimates that the facility is most likely located 80 to 100 meters below the mountain. If true, the complex is located in the deepest location underground of all of Iran's nuclear facilities and would be very difficult to reach with an air strike. IAEA Director Rafael Grossi has repeatedly stated that the organization's inspectors have never been allowed there. Without inspections, the IAEA cannot confirm what equipment is used at Pickaxe Mountain.
Are there uranium enrichment centrifuges at Pickaxe Mountain
In June, the "Wall Street Journal" reported that Israeli intelligence believed "thousands of uranium enrichment centrifuge components" or other sensitive systems may have been moved to the mountain in the months following the 12-day U.S.-Israeli war against Iran a year ago. Donald Trump also commented on this information. He said it was possible, but "there is no evidence." Some analysts also believe the complex could be used to produce or assemble advanced centrifuges if Iran decides to restore or expand those capabilities. The Islamic Republic says the underground complexes are needed to protect its nuclear infrastructure from attack and sabotage. Tehran has repeatedly stressed that uranium enrichment is for peaceful purposes and denies developing nuclear weapons.
International inspectors and intelligence data indicate that Iran possesses about 440 kilograms of uranium enriched to 60%, which is far above the level needed for civilian purposes and close to the 90 percent enrichment needed to produce nuclear weapons.
Bombproof bunker?
Senior fellow at the American Institute for Near East Policy Farzin Nadimi told DW that Pickaxe Mountain is strategically important because it is resistant to bombs that reach underground complexes, but also because it is close to Natanz. According to Nadimi, the strikes on the nuclear complexes in June 2025 have strengthened the importance of this mountain even more.
"Given Iran's security concerns, it can be expected that in the future, uranium enrichment and even weapons-related activities will be carried out in a single, highly protected location," Nadimi said. He said this mountain is the best candidate for such a location. The bunker busting bombs that the US military used in last year's strikes are designed to penetrate the terrain before exploding. But even the most powerful such bombs can only reach a certain depth. Could they destroy a complex dug so deep into a mountain range? The answer to this question is still unclear, as it is not clear exactly how this Iranian complex was built.
Is there any way to disable this facility?
Unlike Natanz and Fordow, which were identified as key to Iran's nuclear program years ago, it is very difficult to assess whether serious damage has been caused to a facility located under a mountain.
Some analysts believe that if the mountain were ever targeted, the goal might not be to destroy the entire complex. A more realistic military objective would be to collapse the tunnels used for entry and disrupt the infrastructure that supports the facility's functions. This would make his job much more difficult.
Whether Pickaxe Mountain will eventually house centrifuges for uranium enrichment, or whether it will simply remain a regular nuclear facility, is still unclear. However, its secret status and apparent size make it one of the most closely watched facilities in Iran's nuclear program, and one that will likely remain important to the international community for many years to come.