H3CX+M9 Gatchina, Leningrad Oblast, Russia
An amazingly interesting structure, whose construction began at the end of the 18th century and was never completed, is still used for its intended purpose: during the hot season, the residents of Gatchina happily bathe in the stone Cold Bath.
Following European fashion, Paul I ordered the creation of a stone pool within the Palace Park where the imperial family and guests could bathe during the summer. There was also an essential condition: the structure had to have columns, pediments, a marble fireplace, or at least a tiled stove.
Construction work started in 1798. A special location was required for this architectural structure. It was found at the point where the winding Kolpanka River flows into the White Lake, in the eastern part of the Topkoy Island. The project of the Cold Bath was designed by the famous Gatchina architect Andreyan Zakharov, and the construction was supervised by Tomazzo Adamini.
By 1800, a small cascade and a rectangular pool lined with polished slabs of Putilovo and Pudost limestone were built. Further plans included constructing a stone pavilion with columns. However, due to the tragic death of Paul I, construction had to be halted.
The unfinished Summer Bath was only remembered at the end of the 19th century. The renowned architect Konstantin Preiss examined the pool basin and proposed his reconstruction project. The master decided to raise the walls and place several marble columns on them, which remained after dismantling the gates at the Engineering Castle. But this project was not approved, and the Cold Bath remained unfinished.
During the war, the structure suffered significant damage. In the 1980s, it was decided to begin major repairs and restoration of the Summer Bath. The cascade and pool structures made of Pudost limestone were replaced with reinforced concrete, but with the onset of perestroika, all work stopped.
The pool basin has survived to this day, but the surrounding area is neglected, and trash is not cleaned up.
Sources:
https://peterburg.center/maps/gatchina-holodnaya-vanna.html
http://gatchinapalace.ru/park/attractions/cold_baths.php