Manjil is known as the windy city of Iran, a reputation it owes to its geographical position in the Alborz mountain range at a small cleft in Alborz that funnels the wind through Manjil to the Qazvin plateau.[4] The biggest wind farm of Iran, the Manjil and Rudbar Wind Farm, is located near Manjil.

Manjil is known for the river Sefīd-Rūd (or "Sepid Rood", "Sefid Rood", "white river"). It passes by the town and is formed in Manjil by two joining rivers. Since 1960 it has been the site of the Manjil Dam that significantly contributes to Gilan's agriculture, such as its olive groves, while generating electric power. The reservoir impounded by the Manjil Dam adds to the beauty of the area Throughout the history Manjil has been a gate to the southern Caspian Sea region. There are numerous archaeological site excavations (mostly illegal) in the Manjil area because of its rich cultural history. Some of these sites are related to the Ismaili era, i.e., Hassan Sabbah movement based in Alamoot forte (one may find artifacts from the 3rd-2nd millennia BC in some households).