You'll want to browse the collections at Erarta Museum and Galleries of Contemporary Art, C-189 Submarine Museum, and Alexander Pushkin Museum and Memorial Apartment. St. Isaac's Cathedral, Admiralty Building, and Strelka are well-known local landmarks worth a visit. You can watch performances at Mariinsky Theatre, Rimsky-Korsakov Conservatory, and Alexandrinsky Theatre if you're interested in local theater.