The castle Alamut was built in 840 AD at 2100 meters above sea level on a rock by Wahsudan ibn Marzuban († 865) from the dynasty of the Djustanids of Dailam.
In 1090 AD, the castle of Alamut was bought by the Assassins and then served as their state headquarters until 1256 AD. Under the assassins the fortress was further expanded and also housed a famous library.
The reign of the Assassins of Alamut was finally ended in 1256 AD by the invading Mongols, who besieged the citadel with a huge army and finally took it by storm, burning down the large library as well.
In 2004 the fortress was severely damaged by an earthquake and is currently being renovated.