Dimitri's hometown Novgorod is misspelled Novgorad in DVD subtitles.
The two nuns in Lorenzo's bath both have bikini tan lines.
The Russian character identifies as a Count, a title not used in Russia until the 18th century.
Count Dzerzhinsky's gun is a 16th-centry musket. Its presence may be an in-joke to the debunked notion that the musket was invented in, and named after, Moscow.
It was nearly impossible for a Russian to travel to Italy in the 14th century, due to the extensive enemy territory and bandit presence between the two countries. A Russian nobleman would seek a wife closer to home.
Most characters pronounce Dzerzhinsky as "Zerzinsky," although the Count himself pronounces it correctly as "Jerjinsky."