Wikipedia
Lake Hjälmaren is Sweden's fourth largest lake. It is situated 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.
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 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 most notably, Pearl Jam.
The rebel Engelbrekt Engelbrektsson, was assassinated in 1436 at Engelbrektsholmen, an islet in Lake Hjälmaren.