Complex sentence: Originally there was a large mosaic panel "Stalin on a tribune" on a prominent wall of the central underground hall, the work of the director of the Academy of Arts of the Soviet Union, Aleksandr Gerasimov.
Split into simpler sentences: Originally there was a large mosaic panel "Stalin on a tribune" located on a prominent wall of the central underground hall. This mosaic was constructed by the director of the Academy of Arts of the Soviet Union, Aleksandr Gerasimov.