Rustaq - Wilayah and town in Al Batinah South, Oman

"Rustaq is a town and Wilayah (District) in Al Batinah Region of northern Oman. The wilayah is in the Western Hajar Mountains, in the south of the Batinah. Rustaq was once the capital of Oman, during the era of Imam Nasir bin Murshid al Ya'arubi. Rustaq Fort, built four centuries prior to the 7th century CE, is an imposing structure built on three levels, containing separate houses, an armoury, a mosque and four towers. The tallest tower stands over 18.5 m (61 ft) high, and has a diameter of 6 m (20 ft). - Wikipedia"