This museum is a treasure-trove of items relating to the Russian theatre including model sets, posters and costumes. You'll have to buy separate tickets to its three sections, the best of which is the Legends of St Petersburg exhibition (R150). Also worth a look is the gallery devoted to the painter, scenery and costume designer Leon Bakst (R100).
A section aimed at children (R80) has great models of the Mariinksy stage and antique contraptions used to create effects like the sound of wind, rain and trains.