Kaliningrad is a seaport city and the administrative center of Kaliningrad Oblast, the Russian exclave between Poland and Lithuania. Before WWII Kaliningrad was the East Prussian city of Königsberg. After World War II Königsberg was placed under Soviet administration and renamed Kaliningrad.
During World War II the city of Königsberg was largely destroyed by a British bombing attack and the Soviet offensive. Here you see a picture from the same point of view as on the postcard.
Königsberg joined the Hanseatic League in 1340 and developed into an important port for the south-eastern Baltic region.