Oman has five World Heritage properties, and all of them are cultural
Background
Oman accepted the World Heritage Convention on 6 October 1981. The UNESCO World Heritage Centre lists five Omani properties and classes every one of them as cultural, so Oman has no natural and no mixed property on the List. They are Bahla Fort, inscribed in 1987; the Archaeological Sites of Bat, Al-Khutm and Al-Ayn, inscribed in 1988; the Land of Frankincense, inscribed in 2000; the Aflaj Irrigation Systems of Oman, inscribed in 2006; and the Ancient City of Qalhat, inscribed in 2018.
In plain words
World Heritage Convention Convention concerning the Protection of the World Cultural and Natural Heritage — The 1972 UNESCO treaty under which states nominate sites for the World Heritage List.