Nizwa Castle was built during the reign of Imam Sultan bin Saif bin Malik Al Yarubi (1649-1679 AD) at the beginning of the eleventh century AH / mid seventeenth century AD, and it took twelve years to build it. It is 34 m high and 45 m in diameter. It serves as a flat-topped platform that was erected on a bedded base with a height of 15 m, and it is said 30 m to the ground. It is equipped with cannon holes. The ascent to the castle is carried out by means of a narrow staircase in the form of the letter (H).