US bombs Iran’s house of secret. What lies beneath Isfahan?

The United States used 2,000-pound bunker-buster bombs to strike Isfahan, known for palaces, tiled mosques, minarets and a stockpile of uranium sufficient to make nine or 10 atomic bombs.

With the name Isfahan tied to Iran's nuclear facilities, the symbolism of an attack there has not gone unnoticed.

President Donald Trump also shared an uncaptioned video on Truth Social showing a series of explosions lighting up the night sky. A US official told WSJ the footage captured the strike in progress.


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Israel’s military confirmed the attack, saying it carried out a large wave of airstrikes across multiple locations in Iran, including Isfahan. “The IDF has completed a large wave of strikes in Isfahan,” the military said, adding that it launched a “wide-scale wave of strikes in several areas in Iran.”

Some analysts say Isfahan had earlier been spared as U.S. and Israeli forces focused on destroying Iran’s air defences, military command centres, and missile and drone systems. Now, the city is back in focus.

ALSO READ: High-risk US plan to extract Iran’s uranium under review by Trump; Netanyahu claims war turning point

The Isfahan mystery

Estimates from a New York Times report suggest Iran holds over 400 kg of uranium enriched to 60%, with much of it believed to be stored in an underground tunnel complex near its Isfahan nuclear facility. This stockpile would be a key step if Iran chose to move toward building a nuclear weapon.

The Isfahan site is a large industrial complex, mostly in the open, making it vulnerable to satellite surveillance and attack.

A tunnel complex lies nearby under a mountain. Satellite analysts have identified three visible entrances—north, middle, and south. During the 12-day campaign last June, the United States and Israel struck the site. Damage to the entrances was visible, but the extent of damage inside the tunnels remains unknown.

This time, clarity on the scale and impact of the strikes on Isfahan is still lacking.

Another concern is that Iran announced, just before the June war, that it would open a new uranium enrichment site in secret. That facility is now believed to be located within the Isfahan tunnel complex.

Just before the current conflict began, the IAEA said it did not know the exact location of the new site or whether it was operational.

Why Isfahan matters now

Trump has repeatedly said Iran must not obtain a nuclear weapon. With Iran under sustained strikes by the U.S. and Israel, the fate of its uranium stockpile—and the question of securing it—has become a key issue for his administration.
Israel’s Prime Minister Benjamin Netanyahu earlier said the decision to go to war was partly driven by Iran moving its nuclear and missile programmes deep underground to make them “immune to any assault.”

The United States chose not to attempt the retrieval of the uranium after last year’s 12-day conflict, with Trump deciding it was too risky at the time.

Ahead of those strikes, Iranian officials took steps to protect nuclear sites, pushing dirt into the entrances of underground facilities, including the Isfahan tunnel network where uranium was believed to be stored.

When the US launched its attacks, it used the Massive Ordnance Penetrator on underground sites at Natanz and Fordo, but relied on Tomahawk cruise missiles to hit Isfahan.

In addition to uranium stockpiles, Isfahan hosts Iran’s test reactor and a facility that converts uranium gas into dense metal, a process known as metallisation, which is a key step in building a nuclear weapon.

Soon after the strikes, high-resolution satellite images showed Iran moving excavation equipment to Isfahan and beginning work to access underground tunnels, according to U.S. officials and others familiar with the intelligence.
The images showed movement of both the soil used to block tunnel entrances and debris caused by the missile strikes.

Analysis by The New York Times’ visual investigations team found similar activity, including digging at multiple locations.

At one site north of the main facility, satellite images showed excavators digging a pit, placing an unidentified object under a tarp, and then burying it. At another site to the northeast, activity increased last month, with images showing what appeared to be a crane loading dirt into a truck.

Satellite images from February also showed large-scale earth movement at several tunnel entrances, including one on the western side. It remains unclear whether the soil was removed or used to reinforce the entrances against future strikes.

Researchers at the Institute for Science and International Security also reported increased activity on roads leading to the tunnels. They said some entrances appeared to be buried, possibly as a protective measure, similar to steps taken before the June 2025 strikes.

(With inputs from NYT)