Hjälmaren

Hjälmaren is the fourth largest lake in Sweden, located in the provinces of Södermanland, Närke and Västmanland. It is connected to Lake Mälaren through the Eskilstunaån river. The lake has a surface area of approximately 484 square kilometers and a maximum depth of 20 meters.

Hjälmaren is known for its many islands, the largest of which is Vinön. Other notable islands include Valen, Blacken, and Stora Risholmen.

Historically, Hjälmaren played an important role in transportation and trade. The Hjälmare Canal, completed in 1639, connected Lake Hjälmaren to Arboga, providing a waterway to the Baltic Sea via Lake Mälaren. Though eventually superseded by railways and larger ships, the canal remains a historical landmark and is navigable for smaller boats.

The lake's ecosystem supports a variety of fish species, including pike, perch, zander, and bream. Fishing is a popular activity on Hjälmaren. The surrounding area is also home to diverse birdlife, making it a significant location for birdwatching.

Environmental concerns, such as eutrophication and pollution, have affected Hjälmaren in the past. Efforts have been made to improve water quality and protect the lake's ecosystem.