German has a very simple way of using place names as adjectives: add the ending –er. Note that no other adjective endings are added, regardless of case or number.
|das Genfer Abkommen||the Geneva Convention||der Hamburger Flughafen||the Hamburg airport|
These adjectives can also be used as nouns:
|der Berliner||the Berliner (male from Berlin)|
|die Berlinerin||the Berliner (female from Berlin)|