You might want to spend some time browsing the exhibits at Erarta Museum and Galleries of Contemporary Art, C-189 Submarine Museum, or Anna Akhmatova Literary and Memorial Museum. Russian Admiralty, St. Isaac's Cathedral, and Admiralty Building are landmarks that you won't want to miss. You can watch performances at Mariinsky Theatre, Rimsky-Korsakov Conservatory, and Alexandrinsky Theatre if you're interested in local theater.