It is home to the Imperial cathedral that contains the burial place of all of the Russian Imperial Tsars.
A special room has been designated for the last Tsar, Nicholas II, and his family (Tsarina Alexandra, daughters Olga, Marie, Tatiana, Anastasia and son Tsarovich Alexei) who were shot to death by their guards and buried in unmarked graves.
It was only recently, nearly 100 years later, that their remains were authenticated by the use of DNA. They were then ceremoniously re-interred in the cathedral with their royal ancestors.
An interesting aside: The DNA used for authentication came from the British Royal Family. Tsar Nicholas’s mother was the sister of Queen Alexandra of England. Tsarina Alexandra was a granddaughter of Queen Victoria. The family resemblance of Nicholas II of Russia and George V of England (a grandson of Victoria and son of Alexandra of England) was very striking and often commented upon.