The major river in this province is the Karaj which originates in the Alborz mountains west of the city of Tehran and is 245 km long. There is an enormous dam built on this river called Amir_Kabir Dam which provides a good part of the province’s potable water and is also used for extensive irrigation. The reservoir behind it is an artificial lake frequently used for water sports and competitions. The reservoir and the river below it provide great opportunities for recreation, and most of the inhabitants of Tehran and Karaj go there on the weekends and other holidays. River Karaj runs along most of the length of the Kraj-Chalous road and attracts thousands of picnickers and campers in summer and spring. Jajrood, 140 km long, is another of the province’s rivers, to the east of the city (of Tehran). There is also a dam on this river known as Latian Dam, which, just as in case of the other, provides a part of the water needed by the province for the inhabitants and for irrigation and offers great recreation opportunities for the people of the city. Lar Dam is the third largest dam in this province. Ab-e-Ali mineral water spring, northeast of Tehran City, Provides water that is rich in calcium bicarbonate. The water from this spring is bottled in a factory close by, and shipped to all parts of Iran. Ab-e-Ali mineral water spring, northeast of Tehran City, Provides water that is rich in calcium bicarbonate. The water from this spring is bottled in a factory close by, and shipped to all parts of Iran. Ghaleh_Dokhtar on Tehran - Amol road and Ask to the west of the city and Larijan hot water springs, are mineral water sources. The province’s frozen waterfall called Yakh_kooh (Ice Mountain) is a unique sight, indeed. The province’s major caves are Golzard close to Lar, Boornik not far from the road to Damavand, and Afshan also close to Damavand. The Alborz mountain range forms a natural boundary that separates Tehran from the provinces that lie on the coast of the Caspian. The highest peak in this range is that of Mount Damavand which 5,636 m high is. This mountain is a dormant volcano and in the crater of the volcano, there is a small lake, some 30 m deep, that is frozen most of the year.