Selsø lies at the end of the little inlet known as Møllekrogen. The lake is separated from the fjord by a sluice, which opens out towards the fjord. The lake is very shallow, with small islands that have been consolidated and enlarged to maintain a habitat for the birds. The lake is bordered on the east by meadows, while the rest is surrounded by reeds. In 1996 the low-lying area north of the lake was inundated and this almost doubled th size of the sanctuary.



Selsø is one of the most exciting bird-watching sites on Zealand. Except for when the lake is frozen over there are always a lot of birds, of many different species, and it is one of the places where it is possible to find rarer species. During the breeding season there are Grebe and (swimming) ducks, and many waders breed here too. Formerly there was also a large colony of Black-headed Gulls, but this has now disappeared, for some unknown reason. Shortly after the establishment of the northern section a large Avocet colony developed there, probably consisting of birds driven away from the islands in the fjord by rats and foxes. In the autumn there are large flocks of Greylag Geese and Wigeon, joined later by Coot and Tufted Duck.

At the southern end of the lake is a bird watching tower with a splendid view over the lake, but the carparks at the northen end of the newly established paart of the lake and by Selsø church are also good places for bird-watching.

In winter you can often see flocks of Whooper Swans and Canada Geese in the fields around the lake.