The series was filmed in Tobolsk and St. Petersburg.
Tobolsk Kremlin
In movie
Scene where Prince Matvey Gagarin is doing business in the Kremlin.
Real
Scene was shot in the Tobolsk Kremlin (Gostiny Dvor), it preserved its original appearance quite well and was perfect for the movie, practically unchanged. There were some minor modifications, but more to preserve the historical truth, for example, the steps in the Kremlin were removed and replaced with an embankment, which is what it was in those days.
Tobolsk
Tobolsk Kremlin