Cisternerne – The Cisterns in Søndermarken

A subterranean world beneath a city park

Buried below the lawns and tree-lined paths of Søndermarken park lies Cisternerne, a vast underground reservoir turned art space directly beneath Frederiksberg Hill. Descending through discreet glass pyramids, you swap daylight for semi-darkness, cool air and the echo of dripping water. The concrete vaults stretch out in long corridors supported by rows of pillars, creating a sense of walking into a hidden cathedral under the city. Covering more than four thousand square metres, the cisterns consist of interconnected chambers that were once completely filled with water. Today, shallow pools, reflections, and a fine mist in the air remind you that this monumental structure was engineered for one essential purpose: securing clean drinking water for a growing capital.

From cholera crisis to engineering marvel

Cisternerne was conceived in the mid‑19th century after serious water supply problems and a devastating cholera outbreak pushed Copenhagen to rethink how it stored and distributed drinking water. Excavation began in 1856, and within three years a new underground reservoir system could hold up to 16 million litres of water, dramatically improving public health and pressure in the pipes reaching upper floors. Originally an open basin, the reservoir was later sealed with a molded concrete roof to reduce contamination risks. For decades it formed a crucial part of the city’s infrastructure until changing technology and new waterworks made it redundant. Its role in the water network ended in 1933, and by 1981 the cisterns were finally drained, leaving behind an empty but extraordinary shell of brick and concrete.

Nature carving a dripstone cave in concrete

Once the water disappeared, a slower transformation began. Moisture seeping through the concrete ceiling dissolved minerals and redeposited them as delicate formations. Over decades this process created stalactites and stalagmites that hang from beams and rise from the floor like something from a natural limestone cave. Cisternerne is now regarded as Denmark’s only real dripstone cave, even though it is entirely man‑made at its core. These dripstones are both beautiful and fragile, a visible sign of the building’s gradual decay. They underline how the structure has shifted from being a tool of human control over water to a space where nature and architecture are entwined. Moving through the chambers, you notice tiny crystal-like fringes along edges and uneven textures on the ceiling where water continues its slow work.

Immersive art in darkness and damp

In the 1990s, the empty cisterns were reborn as an exhibition venue. Initially used as a museum of modern glass art, they have since become part of Frederiksberg Museums and now host one major site-specific art project at a time. Artists are invited to respond to the unusual climate and architecture, often incorporating water, sound and carefully controlled light. Installations may fill sections of the floor with reflective pools, create glowing corridors of color, or add subtle soundscapes that play with the long echo of the vaults. The almost total absence of daylight means that even a single spotlight or lantern feels dramatic. Exhibitions typically run seasonally, with periods of closure in between to prepare the space, so each visit can be a quite different multi-sensory experience.

A sensory encounter in Søndermarken

Visiting Cisternerne is as much about atmosphere as it is about visual art. The temperature hovers around 8–10°C year-round, the air is close to saturated with humidity, and your footsteps reverberate through the chambers. The smell is damp, mineral, and slightly earthy, an underground contrast to the fresh greenery in the park above. The transition from sunlit Søndermarken into the shadowy depths gives the visit a ritual quality: you enter, acclimatise to the gloom, and gradually pick out details in the darkness. Above ground, Frederiksberg Palace and the park’s avenues provide a stately backdrop; below, you explore a former lifeline of the city, now dedicated to contemplation, art and the quiet drama of water, stone, and time.

Planning your time in the cisterns

Cisternerne is compact enough to explore in under an hour, yet rich enough in detail to reward a longer, slower visit. The floor can be wet and uneven in places, and the low lighting encourages a careful pace. Exhibitions may include sound, projections, or small boats and walkways over water, but the core experience remains the same: an immersive, low‑lit journey through a once hidden piece of Copenhagen’s infrastructure, now one of its most atmospheric cultural spaces.