Construction work on Mount Kolang in central Iran, where an underground nuclear complex is believed to be located, has intensified significantly over the past year.
An analysis by the Center for Strategic and International Studies, reported by Romanian news outlet Digi24, showed that building activity accelerated at the location in early 2026. The Washington-based research group reached its conclusions after examining satellite imagery collected over a six-year period.
Analysts observed a transition from heavy excavation work to probable internal construction inside the facility, alongside continued fortification efforts on the exterior. Work near the complex may also include the construction of new access routes, storage buildings, and roads.
The Center for Strategic and International Studies is an independent defense and foreign policy research institute. Uranium enrichment involves processing uranium to increase the concentration of specific isotopes required for nuclear energy production or weapon development.
Centrifuge claims and facility status
Israeli intelligence agencies previously claimed that Iranian authorities relocated centrifuges to the Mount Kolang site. CSIS stated that its assessment neither confirms nor denies the Israeli claims.
Analysts noted that the facility is currently unable to conduct uranium enrichment operations, assuming enrichment is the primary objective of the construction.
Strikes on naval forces
The construction activity comes after United States and Israeli strikes hit key Iranian naval assets during the opening weeks of the conflict in the Persian Gulf. The attacks targeted Iran's submarine fleet, eliminating a capability long regarded as a key pillar of Iranian regional power.
Iran originally purchased three submarines, the Tareq, Nuh, and Yunes, during the 1990s following its conflict with Iraq in order to modernize its fleet and compensate for naval vulnerabilities. The three vessels formed the foundation of Iran's submarine force, designed to lay naval mines, launch torpedoes, and imperil maritime traffic.
The Strait of Hormuz, where the vessels were equipped to operate, is a narrow shipping channel connecting the Persian Gulf to the Gulf of Oman through which a significant portion of global petroleum trade passes.
