Fysingen, Lake in Sigtuna Municipality, Stockholm County, Sweden

Fysingen is a nature reserve containing a lake, wetlands, and open water areas spanning about 184 hectares that draw nearly 100 bird species for nesting. An observation tower with wooden walkways passes through reeds and reaches two viewing decks where visitors can watch the birds and water.

Fysingen and its surrounding land are designated a national interest for scientific nature conservation and cultural heritage. The lake lies in Sigtuna and Upplands Väsby municipalities and drains through Verkaån. Three manor houses stand by its shores: Skånelaholm Castle, Torsåker Castle and Vallstanäs estate.

The lake's name, Fysingen, comes from a dialect word for a small, narrow inlet. Three manor houses stand by its shores: Skånelaholm Castle, Torsåker Castle and Vallstanäs estate. The Fysinge group has recorded 245 bird species around the lake over the years.

The observation tower and wooden walkways are wheelchair accessible and provide safe passage through the reed areas. Spring and autumn months offer the best birdwatching as many species pass through or nest during these seasons.

Fysingen is one of Stockholm County's foremost bird sites: a compilation by the Fysingegruppen lists 245 bird species recorded around the lake over the years. The island Stora Kyngan and part of the Fysingen nature reserve are bird protection areas with no access from 15 April to 30 June.