An ancient doorway within the walls of the Citadel of Arbil. The Citadel is an inhabited mound in the centre of the modern Iraqi city of Erbil, which is said to be one of the oldest, continually inhabited places in the world. Earliest traces of habitation on the mound date back to the 5th millennium BC, possibly earlier. The city of Erbil, the fourth biggest in Iraq, is today the capital of Iraqi Kurdistan. .Since 2007 the High Commission for Erbil Citadel Revitalisation (HCECR) has been in charge of the Citadel complex and is carrying out major reconstruction efforts since moving out all remaining residents. It is hoped that 50 families will move back into the Citadel once renovation work and archeological digs have been completed. .