You might want to spend some time browsing the exhibits at Erarta Museum and Galleries of Contemporary Art, Pushkin Flat-Museum, or Russian Museum. Yusupov Palace, St. Petersburg Academy of Fine Arts, and St. Isaac's Cathedral are well-known local landmarks worth a visit. You can watch performances at Mariinsky Theatre, Bryantsev Youth Theatre, and Tovstonogov Bolshoi Drama Theater if you're interested in local theater.