Copenhagen's Cisternerne: a water reservoir turned art cave beneath Søndermarken park

In Søndermarken park, opposite Frederiksberg Castle in Copenhagen, two glass pyramids poke up from the lawn. They aren't a sculpture: they are the skylights and the entrance to a world lying beneath the feet of passers-by. You descend a staircase and find yourself in the Cisternerne, the old underground reservoir that for decades held the city's drinking water.

The history

Excavation began in 1856 and was completed in about three years. The structure worked as a drinking-water reserve until 1933 and could hold up to 16 million litres. After decommissioning it remained for decades an empty, forgotten volume beneath the park, until it was drained entirely in 1981. Its first public life came in 1996, when Copenhagen was European Capital of Culture and the space was used for the first time as an exhibition venue. Between 2001 and 2013 it housed a museum of glass art; since 2013 it has been a space for contemporary art and is part of the Frederiksbergmuseerne, Frederiksberg's museum network.

The artificial cave

What really strikes you is the physical environment. Water keeps seeping through the concrete ceiling, dissolving the calcareous minerals and depositing them drop by drop: this is why the Cisternerne are considered Denmark's only true cave with calcareous formations (stalactites and stalagmites). The air is cold and damp, the light is scarce, sounds reverberate. It's not a museum in the traditional sense: it's an artificial cavern with puddles, rows of columns and reflections, in which you move through the dark following the artists' interventions.

The installations

Each year the Cisternerne invite an artist or an architect to create a large-scale work conceived specifically for that space. Among the past interventions are "The Water" by the Japanese architect Hiroshi Sambuichi in 2017 and "Event Horizon" by Tomás Saraceno in 2020-21. These are works that use water, darkness and echo as materials, so the experience changes completely from one season to the next: it's worth checking which installation is on before you go.

It's a place overlooked by most tourists for a simple reason: it's underground, in a residential park far from the historic centre and the Little Mermaid, and from the surface all you see are two glass pyramids that many mistake for a park artwork. Those strolling in Søndermarken often have no idea what lies beneath. Precisely for this reason the crowds stay low and you can wander at leisure, though it's best to bring a jacket: inside it's cold all year round.

How to get there

For the visit: the entrance is in Søndermarken, opposite Frederiksberg Castle (postal code 2000 Frederiksberg). The approximate hours are Monday and Tuesday 11-18, Wednesday and Thursday 11-20, Friday to Sunday 11-18, with closure on Mondays in October and November; it's best in any case to check the Frederiksbergmuseerne site before setting out, because hours can change with exhibition changeovers. You get there easily by Copenhagen public transport to the Frederiksberg area and then on foot through the park: the district is well served by metro and buses, and a short walk through the greenery leads straight to the two glass pyramids. Combine it, if you like, with the Frederiksberg gardens right next door.