This is the nearest police station if you need to report a loss or a theft, for example, of documents:
Main station
Breslauer Platz
Additional police stations can be found on the following website: https://koeln.polizei.nrw
Lost Property Office
Citizens’ Center Köln-Kalk
Entrance Dillenburger Straße 25
Ottmar-Pohl-Platz 1
51103 Köln
https://www.stadt-koeln.de/service/adressen/fundbuero
This is where you can find anything that has been lost while riding public transportation. If you lose anything on the S-Bahn or a regional train, please go to Deutsche Bahn's lost and found office.
Main Station Cologne
Trankgasse 11
https://www.fundservice.bahn.com