Sareyn (Persian: سرعین, also Romanized as Sar‘eyn, Sara’eyn, Sar‘eīn, Sar ‘Eyn, and Sarein) is a city in and the capital of Sareyn County, in Ardabil Province, Iran. Sareyn 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 county consists of two districts: the Central District and Sabalan District. The county has one city: Sareyn.
The Sareyn 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.
The word Sareyn in the Persian dictionary means "Spring's Outlet".
The climate and hot springs are the first attractions to tourists who travel to this region from different parts of Iran and the world.
Sareyn is also famous for its 'Ashe Doogh' (Yogurt Soups), during the busy summer periods, it is not uncommon for many of the local shops to be seen selling and preparing this soup.
Hot springs (spa) have always been in Sarein but the 1990s earthquake caused some of them to get colder or hotter. The water is heated largely by the Sabalan mountain which is Iran's second highest mountain after Damavand.
Many tourists visit Sabalan. Its most interesting feat is the 'crater' top which contains a lake of acidic water.
Sareyn is also very famous for its honey, again like the soup, many of Sareyn's shops sell honey which is produced locally by the Bee keepers of the area.
The main language of Sareyn is the Azeri dialect, however Persian is understood.
There are 9 hot springs in Sarein, with 'Gavmesh Goli' being the hottest, with water reaching 67 degrees, and turning out around 80 liters per second from the source. There is also several cold water springs nearby, with the most popular being situated in a small village nearby called 'Vila Dareh' - the water here is fizzy and is very good for the kidneys.
The climate is by far a great asset, and many Iranians from Tehran and other big cities escape to the tranquility and good weather that Sarein has to offer.