Sarein is a city in and the capital of serein County, in Ardabil Province, Iran. Sarein is known for its hot springs. The population is about 8000, and increases to more than 20000 in the summer because of the many tourists who go there due to the charming climate. It stands 28 km from Ardabil and total area is 1.28 square km2. At the 2006 census, its population was 4,478, in 1,135 families. The Sarein springs are near an inactive volcano in mount Sabalan and its water contains Sulphur particles and it is believed that it is good for bone and joint pains.