Like the map?
I have two main characters in my novel. One, Amalie, is a child of Königsberg, East Prussia.
If you look for Königsberg on a current world map you will not find it. In 1945, after World War II ended, the Allies gave the city to the U.S.S.R. To claim it, Joseph Stalin expelled the surviving Germans, renamed it Kaliningrad, and closed the borders. It became a Soviet military base. In spring 1991, Kaliningrad reopened to outside visitors.
To research the history and story of Königsberg/Kaliningrad, I've read:
Before the Storm: Memories of my Youth in Old Prussia by Marion Countess Donhoff
Vanished Kingdoms: The Rise and Fall of States and Nations by Norman Davies
The Fall of Hitler's Fortress City: The Battle for Königsberg by Isabel Denny
Online articles such as The New Soviet Union: Kaliningrad: From Closed Past to Uncertain Future by Michael A. Hiltzik, Times Staff Writer, September 22, 1991
and I follow a facebook page called, My Own Königsberg.
If you have other suggestions for books or articles to read, let me know.