In 1090 CE, Hassan-i Sabbah, the leader of the Assassins, a sect of Nizari Ismailis in Iran, chose the Alamut region as his headquarters to campaign, preach and convert new followers. This proved to be a turning point for the destiny of Alamut Valley. The result of over two centuries of Ismailite stronghold, the region witnessed numerous castles throughout, of which at least 20 "castles" dating back to this era have been identified.