Futuristic & Foreign: Budapest’s Dystopian Underground Reservoir

Rising above the banks of Budapest’s Danube river is Gellért Hill, an affluent residential area with elegant tree-lined streets. But, hidden beneath the surface is a strange and surreal sight - the József Gruber Water Reservoir. Every March, it’s emptied for its annual cleaning. With 106 stretched columns, the second basin makes for a futuristic and dystopian landscape. 

An integral part of Budapest’s water supply system, the reservoir can hold up to 80 million litres of water. Every night, water is filtered and pumped into the reservoir from the Danube river, only to be drained during each day by the residents of Buda. This daily cycle ensures a constant supply of fresh water to approximately 500,000 people.

Construction started in 1970 and took eight years to complete. More than 140,000 cubic metres of earth were excavated from the hillside so the reservoir could be built. Laying the foundations for the two basins required more than 6,000 square metres of concrete, 30cm thick, and it took 25 cement mixer trucks more than 40 hours to deliver concrete without interruption. 

The two basins of the reservoir are each shaped like a piano, a design that serves both form and function. This unique shape, coupled with the 106 columns standing 9 metres tall, prevents water vortices from forming and ensures optimal circulation. The columns are more than mere structural supports; they're hollow and perforated, allowing water to flow through them and further preventing stagnation. This design prevents microorganisms from forming, and ensures the freshness and quality of the water. The facility also employs a state-of-the-art UV disinfection system, adding an extra layer of protection against waterborne pathogens. 

At the time of construction, it was the second largest water reservoir basin in the world, surpassed only by a facility in Tokyo, Japan. 35 years after its construction, József Gruber’s original flow simulations results were confirmed by a computer model. The József Gruber Water Reservoir is open to the public exactly one day a year, March 22nd, which is also World Water Day. On this day, visitors can descend into the drained reservoir and walk among the towering columns, experiencing firsthand the eerie beauty of this hidden underground world.