 Sicklasjön, historically known as "Långsjön" ("Long Lake"), is connected to Järlasjön east of it through a narrow strait and to Hammarby Sjö west of it through the canal and the sluice .The lake, forming the northern border of the Nacka Open-air Area ("Nacka friluftsområde", colloquially known as "Nackareservatet", "Nacka [Nature] Reserve"), is considered as of significant recreational and natural value.Water flow is periodically important but inconsiderable during summers when the lake remains relatively stratified.