Postcode areas 51XXX
- Postcode area 51061 Köln
- Postcode area 51063 Köln
- Postcode area 51065 Köln
- Postcode area 51067 Köln
- Postcode area 51069 Köln
- Postcode area 51103 Köln
- Postcode area 51105 Köln
- Postcode area 51107 Köln
- Postcode area 51109 Köln
- Postcode area 51143 Köln
- Postcode area 51145 Köln
- Postcode area 51147 Köln
- Postcode area 51149 Köln
- Postcode area 51371 Leverkusen
- Postcode area 51373 Leverkusen
- Postcode area 51375 Leverkusen
- Postcode area 51377 Leverkusen
- Postcode area 51379 Leverkusen
- Postcode area 51381 Leverkusen
- Postcode area 51399 Burscheid
- Postcode area 51427 Bergisch Gladbach
- Postcode area 51429 Bergisch Gladbach
- Postcode area 51465 Bergisch Gladbach
- Postcode area 51467 Bergisch Gladbach
- Postcode area 51469 Bergisch Gladbach
- Postcode area 51491 Overath
- Postcode area 51503 Rösrath
- Postcode area 51515 Kürten
- Postcode area 51519 Odenthal
- Postcode area 51545 Waldbröl
- Postcode area 51570 Windeck
- Postcode area 51580 Reichshof
- Postcode area 51588 Nümbrecht
- Postcode area 51597 Morsbach
- Postcode area 51598 Friesenhagen
- Postcode area 51643 Gummersbach
- Postcode area 51645 Gummersbach
- Postcode area 51647 Gummersbach
- Postcode area 51674 Wiehl
- Postcode area 51688 Wipperfürth
- Postcode area 51702 Bergneustadt
- Postcode area 51709 Marienheide
- Postcode area 51766 Engelskirchen
- Postcode area 51789 Lindlar