Sh1n reposted an open-source assessment by @BenTzionMacales reporting renewed excavation at Site 311, a large underground complex near the city of Abyek along the Tehran-Qazvin corridor, roughly 100 km from Tehran.

The facility is excavated into mountainous terrain and has several tunnel portals that may connect to an extensive underground network. Satellite imagery shows large volumes of excavated spoil, supporting infrastructure and substantial rock overburden protecting facilities inside the mountain.

Most excavation took place between 2007 and 2016. Major work then largely ceased, aside from occasional minor progress, and only parts of the complex were brought into use.

Site 311 attracted international attention in 2010 when the Iranian opposition group Mujahedin-e Khalq (MEK) alleged that it was a secret uranium-enrichment facility. That allegation was not independently verified, and there remains no conclusive public evidence that uranium enrichment has occurred there. The site's purpose is unknown; open-source assessments have suggested possible links to Iran's nuclear program, missile infrastructure or other sensitive military activities.

According to the assessment, the operational section of Site 311 was struck by Israel in June 2025 during Operation "Rising Lion" and later again during Operation Epic Fury. The strikes suggested that Israel considered the site strategically significant, although its exact purpose has not been publicly disclosed.

Satellite imagery reportedly showed a clear change immediately after Operation Epic Fury: Iran resumed excavation at a pace not seen at the site in roughly a decade, beginning almost as soon as the bombing ended. The assessment argues that the renewed work may reflect Iran's view that underground construction can protect strategic assets.

An accompanying video shows the reported scale of activity at Site 311 since April.