Hjälmaren

It is bounded by the provinces of Södermanland, Närke, and Västmanland.

Hjälmaren is 63 kilometres long, about 20 kilometres wide, and has an average depth of 6 metres, and a surface of 483 km². The largest towns around the lake is Örebro and Eskilstuna situated at the western and eastern ends of the lake.

Between 1878 and 1887, a damming project lowered the surface level of Hjälmaren 1.3 metres (4.3 ft) to free up land for agriculture and to reduce the risk of flooding.

Rebel Engelbrekt Engelbrektsson was assassinated in 1436 at Engelbrektsholmen, an islet in Lake Hjälmaren.