"Kaliningrad used to be Konigsberg (or Koenigsberg)"
Same difference..."oe" is an alternative way to spell a German word with an o-umlaut (earlier spelled with a little "e" written over the "o"). I don't know how to type the umlaut in this system, but obviously there is a way. (I've seen "o+" used as a way to write the same thing online as well.)