This map by GRID-Arendalin, Norway, shows which areas were most badly affected by Chernobyl disaster. I guess it’s not a coincidence that this map comes from a Scandinavian country, as the wind blew the radioactive clouds in that direction after the disaster happened. I’m suprised about the high levels in Austria though, and the realatively low levels in Hungary, Slovakia, etc. which are situated between Austria and Ukraine. If you have an explanation, don’t hesitate to share.
UPDATE: Well, this video submitted by Ufonaut Rusty might help us with the riddle above: