Underground cathedral in Łódź - monumental water tanks open to visitors

An engineering marvel hidden underground

Monumental drinking water reservoirs hidden underground on Stokowski Hill in Łódź have for years aroused admiration among both specialists and people fascinated by the history of technology. These unique objects, normally filled with water and being an active element of the city's water supply system, are made available to visitors only once every few years, during periodic emptying for maintenance and technical inspections.

This year, the opportunity to enter the interior of these engineering behemoths will be available from October 5 to 30. A total of 6,240 people will be able to cross the threshold of the "underground cathedral" and see with their own eyes the place that has been providing the inhabitants of Łódź with access to clean water for almost a hundred years.

A brilliant plan by an English engineer

The design of the tanks was created at the beginning of the 20th century on the initiative of the English engineer Sir William Heerlein Lindley. It was he who suggested to the Łódź authorities to build a complex of four underground drinking water tanks on one of the highest points of the city - Stokowski Hill, located 260 meters above sea level. Thanks to this, a natural water tower was created, which allows water to flow to the homes of Łódź residents by gravity. The level difference between the water table and the lowest point of the water supply network is almost 100 meters.

The first two tanks, each with a capacity of 15,000 cubic meters, were built between 1934 and 1937, after Lindley's death. Two more were built in 1949–1953. About 2,000 people worked on the construction of the first facilities, including many unemployed textile workers from Łódź. The tanks are made of extremely durable, waterproof brick, and their walls and vaults have a characteristic arch shape, which ensures resistance to the pressure of 60,000 tons of water.

A forest of columns and 15 seconds of powerful echo

Each tank has impressive dimensions - 60 by 60 meters. The vault consists of as many as 100 brick domes supported by 81 massive columns. This "forest of columns" and arched and ribbed vaults make the interior resemble a Gothic cathedral - hence the popular term "underground cathedral". Echoes in these huge rooms carry for up to 12 to 15 seconds.

The water collected in the tanks comes from 19 deep wells. In the event of a failure of all city water intakes, the supplies stored in these brick chambers could supply the inhabitants of Łódź for 24 hours. Interestingly, similar underground tanks designed by Lindley can only be found in Warsaw.

A monument that still works

Although the reservoirs on Stoki no longer have the status of a monument, they still play a key role in the water supply system of Łódź. Their technical solutions and precision of workmanship are respected by both engineers and laymen. Every 2-3 years, during inspections and cleaning, selected lucky people can go down to these underground spaces and see for themselves how unique they are.