You might want to spend some time browsing the exhibits at Grand Maket Russia Interactive Museum, C-189 Submarine Museum, or Erarta Museum and Galleries of Contemporary Art. Yusupov Palace, Mariinsky Palace, and St. Isaac's Cathedral are landmarks that you won't want to miss. You can watch performances at Mariinsky Theater Concert Hall, Mariinsky Theatre, and Alexandrinsky Theatre if you're interested in local theater.