You might want to spend some time browsing the exhibits at Museum of the World Ocean, Bunker Museum, or B-413 Submarine Museum. Ruins of Koenigsberg castle, Amber Museum, and Honey Bridge are monuments to see when you're exploring the area around Cosmonaut Monument. You can watch performances at Kaliningrad Regional Drama Theatre, Kaliningrad Regional Musical Theatre, and Queen Louise Kirsch Puppet Theater if you're interested in local theater.