You'll probably see Cathedral of Christ the Saviour from a distance before you actually find this amazing building. Step inside if it's open or just take in the facade from outside.
You'll soon learn why this Kaliningrad principal church is visited by many travelers. If you're looking for more to see and do here, Immanuel Kant's Grave, Konigsberg Cathedral, and Amber Museum are in the area too. They won't take long to reach from Cathedral of Christ the Saviour.