BBC Verify has spoken to experts and analysed satellite imagery to piece together what we know about the site, and the potential impact of a US strike.

US President Donald Trump has repeatedly threatened to bomb a suspected underground nuclear site in Iran known as Pickaxe Mountain, where recent satellite images appear to show construction work taking place. Pickaxe Mountain is one of the few Iranian sites linked to the country's nuclear programme that has not been the target of US and Israeli strikes. There have been unproven claims that some of Iran's stock of highly enriched uranium may be kept there, which could be further enriched for use in nuclear weapons. "We'll be hitting that area pretty soon, and very heavily," Trump told reporters on 21 July. And on 28 July he said: "I know exactly what's going on at Pickaxe. It's not a big problem - we took out their nuclear sites, and we'll have to take out Pickaxe if we don't make a deal." Iran's foreign ministry spokesperson Esmail Baghaei said on 22 July that "no nuclear activity is taking place" at Pickaxe Mountain, and described US threats as "a fabricated pretext for aggression, destruction, and sabotage". BBC Verify and BBC Persian have spoken to experts and analysed satellite imagery to piece together what we know about the site, and the potential impact of any strike. Kuh-e Kolang, which translates as Pickaxe Mountain, is located immediately south of the Natanz nuclear complex, Iran's largest uranium enrichment facility which has been bombed by both the US and Israel in 2025 and 2026. The site is believed to be buried deep inside the mountain and its exact purpose is shrouded in mystery and speculation. Tehran has previously indicated that it may be a replacement for a building within the Natanz complex used for the assembly of advanced centrifuges that was damaged after a suspected sabotage operation in July 2020.