Per­sian Citadel, part of the Der­bent Fortress in Rus­sia, Repub­lic of Dages­tan. Includ­ed in the UNESCO World Her­itage List. The area of the citadel is 4.5 hectares, the dimen­sions are approx­i­mate­ly 180 meters wide and 255 meters long. The struc­ture is locat­ed on the top of the hill clos­est to the sea. The thick­ness of the walls is 2.5–3.5 m.