元史
The rock of Gerdkuh has a distinct conical shape which rises above the surrounding scree slopes. Apart from the east, the slopes are almost impossible to scale and no defensive works were necessary. The height of the plain surrounding the rock is , and the height of the top of Gerdkuh's fort is . The steepness of the rock and its height has been noted in the work "History of Yuan", which claims no arrows or mangonel stones could reach it.