Siege of Gerdkuh
1253 CE.
Shown on the map at 36.158°, 54.157°.
Gerdkuh was a castle of the Nizari Isma'ili state located near Damghan in the region of Qumis (modern-day Semnan Province of Iran). Gerdkuh is a "fortified mountain"—a high vertical rock of 300 m in height with buildings on its summit and fortifications at its sides, defended by a triple ring of fortifications at its foot, making the citadel impregnable to direct military assault. It was originally a small fort acquired and refortified in 1096 AD by a Seljuq commander who was secretly a Nizari. The fortress served as a place of refuge for the families of the Nizaris, and its strategic location in the middle of the Khorasan Road made it a useful base for collecting taxes from the passing caravans of the Silk Road. Gerdkuh resisted the Mongol invasion of 1253 AD for 17 years, becoming the last Nizari stronghold in Persia to fall. The fortress remained in use until the early Safavid period. Among the major Nizari fortresses, Gerdkuh is the least studied one.
Text from the Wikipedia article Gerdkuh, licensed CC BY-SA 4.0.