The Black Hen, or Living Underground (1981)

Original title: Черная курица, или Подземные жители

At a St. Petersburg boarding school, a new life began for the ten-year-old Alyosha, who was accustomed parental attention. Missing his home, Alyosha created an imaginary magic world of underground dwellers, with a king and his subjects who very much resembled the people surrounding the boy. Alyosha experienced many interesting adventures in this mysterious fairy tale...