If you're a fan of live theater, book yourself a seat for a play at Ploschadka Skorohod. Check online to see what's still available.
You'll have sightseeing choices galore when in St. Petersburg City Centre. Ploschadka Skorohod is a good place to start here, but there are numerous other fine places to consider. State Hermitage Museum and Winter Palace, Church of the Savior on Spilled Blood, and Russian Museum are close to the arts and culture attraction and will round out your day nicely.