Polovtsian Dances
During 1868 Borodin became distracted from initial work on the second symphony by preoccupation with the opera "Prince Igor", which is considered by some to be his most significant work and one of the most important historical Russian operas. It contains the "Polovtsian Dances", often performed as a stand-alone concert work forming what is probably Borodin's best-known composition. Borodin left the opera (and a few other works) incomplete at his death.