Construction work has been speeding up at Iran’s secret Pickaxe Mountain nuclear base, analysts found — as the Trump administration weighs how to pierce through the deep, underground facility.

A six-year satellite analysis of the mountain fortress, located near the Natanz nuclear facility, revealed that construction activity at the site shot up this year — likely in an attempt to transform the site into a safe haven for Iran’s nuclear program, the Washington-based Center for Strategic and International Studies think tank concluded.

“There is a clear surge in construction activity in 2026 that corresponds to the raising and hardening of the portal accesses, paving of the internal road network, reinforcement around access areas, and the flattening and removal of excavation spoil,” the CSIS wrote in its latest report.

More concerning — the site is buried more than 300 feet underground, potentially out of reach of America’s biggest bunker-buster bombs.

Work began speeding up at the Pickaxe Mountain facility in October 2025, the CSIS found, around the time Israeli intelligence warned the Trump administration that Iran was allegedly moving uranium centrifuges and components to the underground base.

While the CSIS could not comment on the Israeli claim, the work being done suggests Iran is attempting to quickly reinforce the base following last year’s June war, where the US and Israel bombed Iran’s nuclear sites.

The work appeared centered on digging out the entrances buried from the attacks, with Iran likely fortifying the entrances to keep the site open from future attacks.

Along with the reinforcement, Iran appeared to be conducting “internal construction,” at the deep mountain base, but the site is still “not yet capable of enrichment work,” the CSIS found.

Tehran also continued the work at Pickaxe Mountain even during the temporary cease-fire with the US under the memorandum of understanding, which was against the terms of the truce, researchers found.

“CSIS imagery analysis confirms that construction activity continued at a high rate during the period covered by the MOU,” the think tank wrote.

The dangers posed by Pickaxe Mountain, buried at least 328 feet under the Kolang Mountain, prompted President Trump to repeatedly threaten strikes at the base.

“We may hit Pickaxe very soon,” Trump told reporters last week.

Destroying the base, however, presents a difficult challenge as its depth keeps it protected from the powerful bunker buster bombs known to be in America’s arsenal.

The GBU-57 is capable of penetrating up to 200 feet underground before exploding, some 130 feet above Pickaxe’s deepest reaches.

American, however, is currently working on developing its next generation penetrator bombs, with secret tests indicating the new bombs could dig through the same type of stone at Pickaxe Mountain, CNN reported.

It is unclear how far along the new penetrator bombs are in development or if they have been fully tested and ready to be rolled out.

The US could also opt to attack the base’s entrances and bury it as it did with Iran’s missile facilities, but experts have noted that the Islamic republic has proven it can dig out its bases time and time again.