The wilayah of Rustaq is in the Western Hajar, in the south of the Batinah. Rustaq was once the capital of Oman, during the era of Imam Nasir bin Murshid al Yaarubi. Rustaq fort, built four centuries prior to the dawn of Islam in Oman, is an imposing structure built on three levels, containing separate houses, an armoury, a mosque and four towers. The tallest tower stands over 18.5m high and has a diameter of 6m.