Mojen is one of the cities of Semnan province. It is situated 35 km northwest of Shahrud, central part of Shahrud city. The population of this city, according to the 2006 census, was 5,528. Due to its location in the mountainous area, the city is dead end and the only transit way to it is an asphalt road which connect Mojen to Shahrud and Gorgan.
Mojen is built in the midst of a fairly large valley between two rivers, Peyhesar and Pishdeh. The occupation of most people is agriculture, horticulture and animal husbandry. Its crops consist of potatoes, wheat and barley, and garden products include apricots, apples, walnuts and cherries.
Mojen has stairway buildings and special architecture (similar to Masuleh). In the old parts of the city, the walls and ceiling of the rooms are decorated with red and yellow soil.
One of the tourist attractions of Semnan province, which is still unknown, is the strait and the waterfall of Dastan, located 7 km west of the city of Mojen in a region called Dashn Teli and Spid Khak. This beautiful and magnificent waterfall flows through a strait called Tangeh Dastan with a height of 12 meters between the two massive rocks. At first glance, the viewer thinks the rocks will collapse any minutes.
This strait is considered by many tourists to be unique, because the form of the rocks and topography of the area has added to its beauty and is a good place for rock climbing. The Tangeh length is about 2 km and its approximate width is 5 meters. On the other side of the river, there are other waterfalls with a height of 5 to 10 meters, the flow of which is very attractive in the Strait.