The southwestern slope of Petrov, originally called Puhlík, once dropped very steeply to the marshy meadow at the Svratka channel. In 1415, the city council agreed with Prokop of Písek, who built the water main in Čáslav, and with a wealthy Brno patron, Václav Haas, to use their money to build a water main from Svratka through Puhlík. The water supply was to feed the fountains in the Upper and Lower Markets, supplying water to the breweries and to individual houses. In 1416, King Wenceslas IV confirmed the agreement and the first water supply was built in Brno. The water was taken from the Svratka channel and driven by a pump at the Lamplův mill (approximately at the site of today’s Kopečná spa) 140 feet (44.2 metres) into the Puhlík reservoir. The pipe system was originally wooden (drilled pipes of pine wood, joined by short iron cylinders); later it was made of stone and iron. The water passed through a complicated system of settling tanks and overflow chambers into wooden reservoirs and then led along Starobrněnská Street into the town.
In 1818, when the Petrov slope was modified to Denisovy sady (Denis Gardens), the old water reservoir was abolished and replaced by a new wooden one. At the same time, two new masonry reservoirs were built on the defence walls and put into operation in 1820. They are still well preserved and can be accessed by a stone gallery along the building, accessible from the garden of the bishopric.
The building consists of two chambers with lengths of 16 metres and 17 metres, at a width of 6 metres. The space has a barrel vault 8 metres above the floor, above which is the garden of the bishopric. In 1873, this waterworks was abolished because the water system was completely rebuilt. The structure has not been used since and is gradually deteriorating. However, these spaces, reminiscent of an empty cathedral, directly invite architects and builders to reflect on their possible future use.