Cisternerne – The Cisterns in Søndermarken

An underground world beneath Søndermarken

Deep below the grass and trees of Søndermarken, Cisternerne stretches out as a vast concrete cavern that once held 16 million litres of drinking water for Copenhagen. Built in the 19th century as part of the city’s water supply, the reservoir was drained in the late 1900s, revealing an eerie forest of pillars and vaulted chambers. Today, only two glass pyramids on the surface give away the presence of this world below, where you descend by staircase into semi-darkness. Inside, the temperature stays at around 8–10°C year‑round, with humidity close to 100%. Thin films of water bead on the walls, and slow drips from the ceiling have gradually formed small stalactites. The space feels at once industrial and geological, as if part infrastructure, part natural cave.

From city reservoir to atmospheric art space

Once the tanks were decommissioned, the sheer drama of the architecture inspired their reinvention as an exhibition venue. Cisternerne now belongs to Frederiksberg Museums and functions as an underground stage for ambitious contemporary art. Each season, a single invited artist or architect takes over the entire 4,400 m² space, creating an installation conceived specifically for its darkness, echo and damp air. Works often respond to themes of water, climate and deep time, making use of reflections in shallow pools, controlled mist, soundscapes and carefully choreographed light. Some past exhibitions have involved moving through sections by boat or along narrow walkways, sharpening the sense that you have left the everyday city behind. The result is not a gallery of separate pieces, but a total environment that surrounds you.

Climate, sound and sensory immersion

One of the most striking aspects of Cisternerne is its climate. Even on the hottest summer day, the air underground feels cold and saturated, and your breath mingles with a light fog that hovers in the vaults. Footsteps reverberate along the aisles, and sounds from the art – recorded voices, low drones, trickling water – echo off the concrete, turning the entire reservoir into a resonant instrument. Light is scarce and carefully controlled. Pools of illumination pick out columns or artwork, while other zones are left in near darkness, forcing your eyes to adjust slowly. The interplay of light and shadow, punctuated by drips from the ceiling, creates a dreamlike, almost cinematic atmosphere. Time seems to stretch as you wander, aided by the lack of daylight and any visible connection to the outside world.

History, engineering and the city above

Beyond its role as an art venue, Cisternerne tells the story of Copenhagen’s transformation into a modern city. The reservoir is a monument to engineering and public health, built to secure clean water at a time when urban growth demanded new infrastructure. Walking between the massive pillars, you can still read the logic of the original basins and channels that once channelled water beneath Frederiksberg Hill. At the same time, the surrounding park and nearby Frederiksberg Castle hint at an older layer of urban history above. The contrast between the open lawns and the buried reservoir illustrates how the city has been built in strata, with Cisternerne occupying a hidden, in‑between layer. Exhibitions often draw on this context, connecting the underground space to environmental, social or historical questions.

Planning your visit inside the cisterns

A visit inside typically takes 45–90 minutes, depending on how long you linger with the current installation. Entry is ticketed, with standard adult admission in the low‑to‑mid range for Copenhagen museums, and free entry for young children is common. The site usually opens seasonally from mid‑March to late November, often remaining closed during the darkest winter months to prepare new exhibitions. Practical preparation matters here more than at many museums. The stable underground chill means you should bring an extra layer, even in summer, and shoes that handle damp floors. The space is reached by stairs and has limited facilities – there are no toilets inside the cistern halls themselves and no natural light, so it can feel intense for very young children or visitors sensitive to darkness. Many people combine a visit with a walk in Søndermarken or the neighbouring Frederiksberg Gardens, making the underground experience part of a broader day outdoors.

Who will enjoy Cisternerne

Cisternerne particularly rewards travellers interested in contemporary art, unusual architecture and atmospheric spaces. It suits curious adults, teens and older children who enjoy immersive experiences rather than traditional displays in glass cases. Photographers find moody compositions in the columns, reflections and mist, though tripods are usually restricted. It is also an evocative stop for couples exploring Frederiksberg, or solo travellers looking for a quieter, contemplative corner of the city. Even if you are not deeply versed in art, the play of sound, water and light is immediately accessible. What stays with most visitors is the feeling of having stepped into an underground cathedral where the city’s practical past has been transformed into a space for reflection and imagination.