It covers 40,72 km2 (15.39 sq mi) and is situated on the island of Zealand 43 kilometers (27 miles) 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.

The artificial canal was begun around 1717 by royal command, and the work was carried out by Danish soldiers and Swedish POWs.

Historically, Arresø was a fjord, having extended northwards as Brødemose Sund, connected to Kattegat, but the land northwest of here rose after the last Ice Age, locking the waters in and creating the lake.

[1] The renovated wooden ship M/S Frederikke offers boat tours on the lake between May and September, embarking from Arresødal.