If your trip to St. Petersburg is all sorted out but your itinerary is a bit on the empty side, let us give you a few hints and tips.Experience the best that this place has to offer by adding Palace Square and State Hermitage Museum and Winter Palace to your to-do list. If you have an extra day or two to spare, check out Church of the Savior on Spilled Blood and Kazan Cathedral as well.Near the city center, Mariinsky Theatre is one spot you might like to add to your to-do list. C-189 Submarine Museum and Yusupov Palace are also nearby and worth checking out.