Lake · Denmark
Arresø
Arresø is the largest lake in Denmark. It lies on the island of Zealand, about 43 km north-west of Copenhagen, and it is very shallow: on average only about 3 metres deep.
Picture credit: Henrik Buhl (CC BY 3.0) · Kresten Hartvig Klit (CC BY-SA 2.5) · hbuhl (CC BY 3.0) · Wikimedia Commons
Where is Arresø?
Countries on its shores: Denmark.
Largest lake of: Denmark.
Middle of the lake: 56.00° N, 12.07° E
The story behind it
About 4 000 years ago, Arresø was not a lake at all but a fjord – a long arm of the sea joined to the Kattegat. After the last Ice Age the land slowly rose, the water was cut off from the sea, and the lake was born. Today its most important inflow is the small river Pøleå. Around 1717, by order of the king, Danish soldiers and Swedish prisoners of war began digging the Arresø Canal, which carries the lake's water to Roskilde Fjord. Even at its deepest point the lake is only 5.6 metres deep. Many birds live around the lake: sea eagles have come back to build their nests, and beavers have been brought back too. The town of Frederiksværk and the village of Ølsted lie near the shore. With about 40 km² of water, Arresø is the biggest lake in all of Denmark.
Find it on the globe
Arresø is there as a small blue dot with its name, right on the water. From far away the planet is only a blue ball; detail arrives as you zoom in, and this one appears once you are close enough. Open it on the globe.
It sits at its real coordinates, not near them — the same numbers listed in the facts above. Switch off the layer for this kind of place and it disappears again; the buttons for that are down the right-hand edge.
Questions children ask
How big is Arresø?
Arresø covers about 40 km² – sources give between 39.9 and 40.7 km². That makes it the largest lake in Denmark.
How did Arresø form?
It used to be a fjord, an arm of the sea joined to the Kattegat. After the last Ice Age the land rose and cut the water off from the sea, so it became a lake.
Where does the water of Arresø go?
It flows out through the Arresø Canal into Roskilde Fjord. People began digging this canal around 1717.
Where these numbers come from
Every figure on this page was checked against public reference sources before publication. Where sources genuinely disagree, the text says so.
Last checked: