Not the worst, but quite interesting
Niederhein, Germany. It is a former British RAF base, the airport itself converted for commercial flights with a brand new terminal building. But that's not what makes it interesting.
The entire base is still there: homes, shops, theater, everything. On your way to or from the terminal, you drive through a ghost town. Some of the shops still have the latest sale posters on the windows, the theater still has the "what's playing now" billboard up. Ít made quite an impression on me.