What is "altasjon"

Ältasjön ( Swedish: "Lake of Älta") is a lake in southern Stockholm, Sweden, located north-east of Lake Flaten and named for the vicinity to the urban district Älta.

Ältasjön, of which the easternmost fourth belongs to the Stockholm Municipality and the rest to Nacka Municipality, is the uppermost lake in the Sicklaån water system which also include Ulvsjön, Söderbysjön, Dammtorpssjön, Källtorpssjön, Järlasjön, and Sicklasjön. The lake has a rich bird life and, bordering the Nacka Open-air Area (colloquially referred to as Nackareservatet, "Nacka [Nature] Reserve", but not given the status of a reserve), is used for bathing, camping, bird-watching, and water-skiing and is considered as of great recreational value. High levels of chlorophyll reduces clearity, but, notwithstanding the traffic route passing nearby, metal levels are lower than in any other lake in Stockholm.

The "Save Ältasjön Society", Föreningen Rädda Ältasjön (FRÄS), has been working since 1975 to improve the environmental state of the lake and promote open-air activities in and around it.