Semnan city with an area of about 22120 square kilometers is the center of the province. This city is limited from the north to the ridge of the Alborz mountain range, from the south to the central desert plain, from the east to Damghan city, and from the west to Aradan and Firouzkoh. Semnan city is the capital of Semnan province.

This city is located 205 kilometers east of Tehran and on the road from Tehran to Khorasan. And its height is 1117 meters above sea level. This city has long been one of the cities of the fourteenth historical state (Verne) or (Verne) of the 16 ancient divisions. Some researchers and historians considered this city to be among the states of the Medes, and some others were among the states of the Parthians.
The researchers of Semnan know about the dialects. There is a special variety of dialects in this region, and even in the neighborhoods, there are differences in the type of dialects. The natives of Semnan region are called Semnan
Some believe that this name is derived from (‌shaman)‌ Some others believe that the name of this area is derived from the names of two tombs of the prophets in the northeast of Semnan, named Sim Nabi and Lam Nabi, which was changed to Seman over time.