Hjälmaren
 Lake Hjälmaren (Swedish pronunciation: [ˈjɛlːmaren]) 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.