Arresø

Arresø is the largest lake, by area, in Denmark. It covers 40,72 km² and is situated on the island of Zealand 43 kilometers northwest of Copenhagen as the crow flies.

Arresø is located in the northern parts of Zealand in the region of Hovedstaden just north of Ølsted and east of Frederiksværk. It is a part of the three municipalities Gribskov, Halsnæs, and Hillerød. The lake empties into Roskilde Fjord through the Arresø Canal in Frederiksværk. The artificial canal was begun around 1717 by royal command, and the work was carried out by Danish soldiers and Swedish POWs.

There are a number of rivers and streams running into Arresø of which the Pøleå is the most significant. The landscape is especially hilly along the lake's west side.