Fearing an attack from its enemies, Iran has deliberately chosen to keep its nuclear programme scattered.
Uranium is mined at a number of facilities in eastern and southern Iran, then shipped to other sites, notably Fordo and Natanz, for enrichment. The country has one operational nuclear reactor, in Bushehr, with another under construction.
Many of these facilities have also been the site of mysterious incidents - assassinations and explosions - over the past few years. The culprits are rarely identified. Iran has blamed the attacks on Israel and the United States.
Washington has denied any responsibility; Israel refuses to confirm or deny its involvement.
Click on the markers on the map below for more information about Iran's nuclear facilities.