Lambsar or Lemsar Fort located in the north of Qazvin and in the Alamut area in the northeastern part of Razmian city, dates back to the Sassanid era and was used extensively in the Seljuk period. This castle is one of the most important bases of the Ismailia after the fort of Hasan Sabah and is located in the western part of Alamut in the city of Qazvin. Unfortunately, the year of construction of this building is not mention in the historical documents. The castle measures approximately 480 meters in the north-south direction and 190 meters in the east-west direction.
The huge double layer walls with an elevation of more than 10 meters from the huge stones, which are now the only remaining remnants of it remained, was to protect the castle against the attack of enemies. Amazing things about this castle are the amazing mechanism of collecting and storing rainwater, water supply systems, and tanks of cereals in the south and southeast that has been able to survive despite the long-term blockage of its inhabitants.
This castle, located in the western part of Alamut, was the most important headquarters to defend Alamut against the West’s invasion. The year of construction of the castle building has not been incorporated into historical texts, but the type of construction and materials used in it indicate that the fortifications of the Sassanid period and the early centuries of Islam. The castle was famous for its position and importance during Isma’ili domination and was one of the most important Ismaili fortresses after the Alamut Castle in the village of Gazarkhan.