Once upon a time in Siberia takes us on the shooting of Serko, a long feature film directed by Joël Farges. Serko tells the story of a young Cossack who, in 1889, crossed the frozen Siberia, riding his horse named Serko, in order to meet the Tsar and claim more justice for Siberian people. From Lake Baïkal to Saint Petersbourg, how were the horses trained to act in the film ?—Prud'homme, Olga