The United States is planning what have been described as “decisive strikes” against Iran’s underground nuclear facilities after a “clear surge in construction activity” was detected this year near the Natanz nuclear complex, around 140 miles south of Tehran, according to CNN.
On Wednesday, President Donald Trump threatened to escalate military action against Iran, claiming the country would be “bombed at a much greater rate” and would “never be able to get back up”. He also raised the possibility of striking the site known as “Mount Pickaxe” after activity and movement were detected there, warning Tehran not to attempt anything.
Surge in Construction Activity
According to a new analysis of satellite imagery conducted by the Center for Strategic and International Studies, or CSIS, and shared exclusively with CNN, the site has witnessed a “clear surge in construction activity” this year.
After Israeli intelligence claimed that Iran was seeking to move centrifuges to the site as part of uranium enrichment efforts, the CSIS team concluded that the granite mountain would be extremely difficult to destroy even with the heaviest non-nuclear bombs currently available to the Pentagon.
It is also not the only Iranian nuclear facility feared to be beyond the reach of the current generation of American weapons, while indications suggest that the United States is working to develop new means of striking such sites.
CNN reported that four days before the war against Iran began, a programme director at an obscure Pentagon agency responsible for countering weapons of mass destruction signed an emergency contract worth $1.2 million.
According to the available information, the contract called for repairs to a unique underground missile testing facility at White Sands, New Mexico, in preparation for “a live-fire test intended to validate classified capabilities against rapidly emerging threats”.
Rapid Preparations for a Bomb Test
CSIS analysts believe the deeply buried Iranian facility was most likely designed to serve as a secure refuge for the country’s nuclear programme.
A document issued by the US Defense Threat Reduction Agency was entered into a federal database on 27 February, one day before the war began.
The memorandum stated that “rapid test preparation” had to be completed within two to three weeks in response to “a national security directive governed by a compressed timeline”.
Three sources familiar with the matter told CNN that the testing plans were connected to the war with Iran and to the need to develop a means of destroying Iranian facilities buried deep underground. The tests were also intended to simulate possible US strikes against specific nuclear sites.
Granite Rock Similar to Mount Pickaxe
After the United States carried out strikes on Iranian nuclear sites in June 2025, an American general told lawmakers last year that the nuclear site in Isfahan had only had its entrances buried because the Pentagon assessed that its bunker-busting bombs would not be capable of completely destroying the facility.
The US military subsequently began developing a “next-generation penetrator” bomb as a replacement for the current Massive Ordnance Penetrator, or MOP, potentially enabling it to strike targets buried at greater depths.
Satellite imagery shows that between 16 and 18 February, excavation work began at a remote site in White Sands operated by the Defense Threat Reduction Agency and US Strategic Command. The facility is used to test the effects of weapons against deeply buried targets.
The timing coincided with the emergency contract. Construction company BAT submitted an estimate for the testing work on 17 February and was awarded the contract the following day.
According to an environmental assessment, the White Sands test site is also excavated into granite rock, similar to the geology of Mount Pickaxe.
A source familiar with the matter said the US military maintains operational plans for strikes against Mount Pickaxe, which had formed part of a package of potential targets under consideration earlier this summer when Trump was threatening to escalate the confrontation with Iran.
A Potential Nuclear Safe Haven
The source said the strike plan for Mount Pickaxe involved the use of some of the largest bombs in the US arsenal.
However, it remains unclear whether those munitions would be capable of penetrating deeply enough underground to destroy any facilities or equipment Iran may have moved there.
According to the CSIS analysis, the Mount Pickaxe facility was “likely” designed for one of three purposes, all connected to Iran’s nuclear programme: a centrifuge assembly facility, an enrichment facility, or a secure site for converting uranium into metal.
In their report, CSIS analysts said construction at the site “appears to have shifted from active excavation to a phase likely involving internal construction and continued reinforcement of external fortifications”.
The report said Mount Pickaxe had seen “increased roadwork activity” during 2026 at levels greater than at any previous point. Additional work included “raising and fortifying tunnel entrances, paving the internal road network, and reinforcing areas surrounding the entrances”.
The analysts also warned that the “continuing construction activity” observed at the site, alongside other factors, indicates that it is “not yet ready for enrichment operations, if that is its intended purpose”.
What Is Mount Pickaxe?
Mount Pickaxe is a deeply buried facility south of Tehran, within the Zagros mountain range in Isfahan Province and close to the Natanz nuclear facility. It is known locally as Kuh Kolang.
Western intelligence assessments indicate that the site contains four main entrances, two on the eastern side and two on the western side, each measuring around six metres wide and eight metres high.
Estimates suggest the facility may be excavated as deep as 600 metres beneath layers of solid granite, potentially placing it beyond the reach of even the most powerful American bunker-busting bombs, including the GBU-57 used in recent strikes.
Since construction of the site began in earnest in 2020, Tehran has maintained that it is nothing more than a facility for assembling and manufacturing advanced centrifuges.
Iran also insists that its nuclear programme is intended for peaceful purposes and remains subject to monitoring by the International Atomic Energy Agency.
