IAEA teams have combed Iran for years and have around-the-clock monitoring systems at main sites such as the Russian-built reactor at Bushehr on the Gulf coast and the biggest enrichment facility at Natanz in central Iran. Inspectors also have visited a once-secret enrichment lab, known as Fordo, built into a mountainside south of Tehran after it was disclosed in 2009.
But some areas remain off-limits despite repeated demands from the IAEA.
Chief among them is the Parchin military base outside Tehran, which has been visited by IAEA inspectors in the past.