CNN reported Wednesday that construction activity surged in 2025 at Kuh-e Kolang Gaz Lanjeh, an underground site in Iran linked to Tehran’s nuclear program. The report is based on satellite imagery analysis by the Center for Strategic and International Studies (CSIS).
According to the report, a team of experts examined satellite images collected over six years and identified a significant acceleration in work at the site over the past year. The activity included reinforcing tunnel entrances, paving internal roads, strengthening access areas, and removing piles of earth created during tunnel excavation.
Kuh-e Kolang Gaz Lanjeh is located in the Zagros Mountains, near the Natanz nuclear facility, and is considered one of the most sensitive sites in Iran’s nuclear program. According to experts quoted in the report, the underground facility may be exceptionally deep and fortified—potentially difficult to strike even with bunker-buster bombs.
The report comes after U.S. President Donald Trump threatened in recent months to attack the site, which according to Western reports may be used by Iran for uranium enrichment or storing sensitive nuclear equipment.
CSIS noted that satellite imagery alone cannot definitively determine the purpose of the work at the site, but emphasized that the activity pattern indicates a shift from excavation and earthworks to a phase of reinforcement and internal construction—all against the backdrop of ongoing tensions surrounding Iran’s nuclear program.