|Max. length||58 km (36 mi)|
|Max. width||18 km (11 mi)|
|Surface area||483 km2 (186 sq mi)|
|Average depth||6.2 m (20 ft)|
|Max. depth||20 m (66 ft)|
|Water volume||3 km3 (2,400,000 acre⋅ft)|
Hjälmaren (Swedish pronunciation: [²jɛlːmarɛn] or [²jɛlːmaɳ]), also spelled Jälmaren, is Sweden's fourth largest lake. It is situated in the Central Swedish lowland adjacent to Lake Mälaren through which it drains into the Baltic Sea, west of Stockholm. It is connected by waterway with Stockholm by the 13 kilometres long Hjälmare kanal.
Hjälmaren is 63 kilometres long, about 20 kilometres wide, and has an average depth of 6 metres, and a surface of 483 km². The town of Örebro is situated at the western end of the lake. The lake, however, has become an iconic part of Sweden with music festivals taking place on the banks of the lake. Such notable bands to play there are The Smashing Pumpkins, Sonic Youth and Pearl Jam.
1878 until 1887 the project Hjälmarsänkningen lowered the surface level of Hjälmaren 1.3m to free up land for agriculture and to reduce the risk of flooding.
The rebel Engelbrekt Engelbrektsson, was assassinated in 1436 at Engelbrektsholmen, an islet in Lake Hjälmaren.
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