The Bahla Fort was built during the 13th – 14th century. It was built of mud bricks and stone. Bahla Fort is an example of the power of the Banu Nebhan tribe. It is considered as the oldest fort in Oman. It was registered as the UNESCO World Heritage Site in 1987, in fact, on the UNESCO list of the most endangered monuments. The restoration work began in 1990, and was completed in 1999. It was open for the public and removed from the list of the most endangered UNESCO sites in 2004.