Maridalsvannet

The lake and its role

Maridalsvannet sits at 149 metres above sea level between Nordmarka and Lillomarka, within Oslo’s municipal boundary. At roughly 3.7 square kilometres, it is the city’s largest lake and its principal drinking-water source. The Skjærsjøelva and Dausjøelva feed the lake; at its south end, water leaves as the Akerselva.

This is not a swimming lake or a waterfront picnic spot. Its value lies in the scale of the water, the surrounding forest and fields, and the clear sense of Oslo’s water system meeting the city’s outdoor landscape.

Walking the surroundings

Use the roads and trails around the lake rather than treating the shore as an access area. The southern side links into the trail network of Oslomarka and makes a natural start for a longer walk following the Akerselva downhill.

A practical option is to begin near the lake’s southern end and continue south towards Frysja and the river. From there, the character changes quickly: wooded upper banks give way to the former mill and factory corridor of Akerselva.

For a shorter visit: walk a section of the south-side paths for open views across the reservoir, then return the same way. The lake is large enough that a full circuit is a commitment rather than a casual promenade.

Access and connections

Kjelsås is the useful transport-side gateway for the southern end: tram, bus and rail stops are within walking distance of paths leading towards the lake. The Gjørvik Line also follows the eastern side of the water.

The terrain is outdoor rather than urban. Expect unpaved paths in places, variable footing after rain, and snow or ice in winter. Choose footwear for forest tracks if heading beyond the roadside viewpoints.

Protected drinking water: essential rules

The restrictions here are unusually strict because Maridalsvannet supplies Oslo’s drinking water. Within the marked restriction area, swimming, fishing, boating and any activity that pollutes the water are prohibited.

Also keep these rules in mind:

• Do not rest within 50 metres of the lake, streams or rivers.
• Do not camp on slopes down towards the water; this includes hammocks.
• Keep dogs on leash within 50 metres of water and remove dog waste.
• Do not feed birds.

Follow posted boundaries and use the paths as through-routes. The lake is best understood as a protected working reservoir, not a recreational water body.