Nizwa Fort Castle
Nizwa Fort castle is one of the largest, most attractive and visited national monuments in Ad Dakhiliya governorate. It is a well-known tourist destination with a historic walking area which was built by Imam Sultan Bin Saif Al Ya'rubi, the second Ya’rubi, in the 1650s, although its underlying structure is related to 12th century. The interesting point is that it was built above an underground stream and it took 12 years to complete