Hasan-i-Sabbah led the Ismaili dawa from the castle of Alamut, which was built on top of an unassailable granite rock on one of the peaks of the Alburz range, 100km north of modern Tehran. It is located in the south of Caspian Sea in the province of Daylaman in the Rudbar region near the city of Qazwin. Photograph: (Late) Ali M. Rajput.