During the Empire of Trebizond, many new structures were built. One is Kiz Castle in Rize Province. The castle sits on an islet just off the Black Sea coast. According to Anthony Bryer, a British Byzantinist, it was built in the 1200s or 1300s on the order of Trapezuntine rulers. Zilkale Castle is another fortress in Rize Province. According to the same historian, it may have been built by the Empire of Trebizond for local Hemshin rulers. Yet another fortress, the Kov Castle in Gümüşhane Province, may have been built by Trapezuntine Emperor Alexios III.