Continuing the week's theme of Germany's floating frontiers, Neil MacGregor visits two cities now beyond Germany's present borders, but which played important roles in Germany's intellectual and literary history. Kaliningrad, on the Baltic, became part of the Soviet Union in 1945, and is now part of Russia. But for centuries it was Königsberg, a major Prussian city, and birthplace of the philosopher Immanuel Kant - and so central to the intellectual history of Germany. Neil also visits the Czech city of Prague, once home to a large German-speaking community, which included Franz Kafka, one of the most acclaimed writers in the German language. Today neither Russian-speaking Kaliningrad nor Czech-speaking Prague are in any sense German - but what is their place within the memories of Germany? Producer Paul Kobrak.