When I was in Saint-Petersburg last November I briefly met a friend of a guy called Nikita Slavin.
He had a cool project involving mapping out the age of 55,000 buildings in Saint-Petersburg. TLDR, Saint-Petersburg is really the city of Nicholas II – an absolute majority of buildings in the center were built during the 1900-1916 period.
As you can see from the statistics bar at the bottom, the pace of construction would not exceed Tsarist levels until mass khrushchevki came along from the 1950s.
Anyhow, I am happy to see that his project has recently culminated.
Here is the map itself: https://how-old-is-this.house/
And here is a longread (in Russian) on how he made it: https://how-old-is-this.house/process