The former home of Prince Yusupov, whose family was the wealthiest in Russia, even richer than the Tsar. He was one of several who plotted to assassinate Grigory Rasputin, whose influence on the Tsar's family, owing to the hemophilia of their son, was deemed to be excessive.
Lured to the Palace on the pretext of socializing with the Prince's wife, Irina, co-conspirators played music and acted as though there were a large party taking place upstairs...
...while Rasputin was treated to cyanide-laced cakes belowstairs. When they failed to have the intended effect. Prince Yusupov shot Rasputin, although he managed to make it to the courtyard, where he was shot sevral more times. The assassins seem to have been singularly inept, tho, as this did not finish the job, so they tied the monk up and dropped him through a hole in the ice in the river. The postmortem showed he drowned trying to break through the ice.
The Prince's family were not executed, as they might have been had they not been so rich and influential, but they were exiled to the Crimea, and had to leave behind this lovely home.