This dam with its ancient and large barricade is located in Nimvar (Mahalat). The same dates back to the Sassanide period or according to some narrations to even before the birth of Christ. The dam is approximately 100 m. in length and 9 m. in width. The materials used for construction are generally huge slabs of stone and mortar. But in spite of its antiquity, the dam has retained its former fortifications. As most of the water streams of the region are seasonal, the Nimvar Dam acts as a reservoir for the water of the Qom Rood River and guides it to the Nimvar stream.
The dam water seeps in a way through its walls to the bed of the Nimvar stream. Thus being utilized for irrigation purposes in the area. Surrounding this archaeological dam are recreational spots. In addition to this reputed dam, there are other barricades or dykes such as La'lian, Jordan and Baqer Abad in Mahalat and Javadieh, Lood, Darreh Garm, Ashna Khor and Qorveh Kahrizak in the township of Khomein.These are historical relics of the country.