Kalat-e Naderi is an elevated, isolated plateau in the mountains of Khorasan, some 150 km north of Mašhad, edged with steep cliffs that transform it into an almost inaccessible natural fortress.
Geologically, it is in a synclinal enclave, thrust into relief by differential erosion of the Upper Cretaceous sedimentary series.
Basically oval in overall shape, over 30 km long with an average width of 8 to 12 km, it reaches heights of some 900 to 1100 meters at the high points of the edges, which dominate the outer flanks with continuous sheer hard limestone cliff walls rising 100 to 200 meters above a talus of soft rock formed in the surrounding subsurface.
Such an unusually high place, and its defensive value, did not fail to be exploited from very early on. Several references to kalāt in the tragic episode of the young Forud in Ferdowsi’s Šāh-nāma are thought to refer to this location. Its earliest mention in historical accounts comes from the Mongol period, when the fourth Il-khan of Iran, Arḡun Khan, who sought refuge there after being defeated by his uncle Aḥmad Takudār, built a defensive work at the south approach that still bears his name.
It was Nāder, born in the nearby Darra Gaz and well aware of the importance of this location, who fitted out the buildings systematically upon his return from India by fortifying all the approaches with new construction, with the intent of making it a major support center for his power, a possible launching point against the Uzbeks, and, according to oral tradition, a secure place to deposit his riches. Perhaps this was the original purpose of the building known as the Maqbara-ye Nāder, which he had built in the valley, some 5 km from the southern entry, comprising a tower about 20 m high and 12 m in diameter, whose walls were faced with pilasters.