Nordre Øyeren Nature Reserve

Nordre Øyeren Nature Reserve is a large protected area encompassing the largest inland delta in Northern Europe. It is found on the north end of a lake called Øyeren, a bit east of Oslo and close to the town of Lillestrøm. It is 62,6 km² in size. 55,1 km² of the reserve is water, with the rest being delta plains, islands and a few mainland forest habitats. It is well known for its high diversity in species of both flora and fauna. Øyeren is the lake with the highest number of fresh water fish species in Norway (25 species). 

There are three different rivers that flow into Øyeren, which then creates the delta. These are Glomma (the largest river in Norway), Nitelva, and Leira. The reserve was established in 1975, and declared a Ramsar site in 1985 because of its importance for migrating birds. 269 species of bird have been recorded here, making it one of the top spots for birding in the region. The reserve is also home to 18 species of mammal, with moose and roe deer being among the larger species. It is also well-known for its healthy beaver population.