I am just reading a book about Eastern Prussia and Koeningsberg was one of these places with a Teutonic Castle that did not survive the end of the war since it was chosen to be the fortress of defending Nazi.
Koeningsberg as the place changed completely. It is not German anymore, but rather Russian enclave to the West. Times of Emmanuel Kant are gone
Here is the history of the castle before and after the distraction are here: