A lake in Sweden.
The largest lake in the Dalarna county and Sweden's seventh by size.
About 36 Km long and 25 Km wide. Its maximum depth is about 128 meters. The water level is regulated via the Gagnef Lock.
Before the railway's advent, the lake was an important water way in the region, especially for the transport of iron ore.
The Siljan freezes over around the first days of January, and it thaws in May.
The name Siljan is thought to have its origin in the Old Swedish word 'sil', meaning calm water, or in the word 'sylghir', thought to have meant 'the swallower'.
Sources: various on the 'net