Oldest first. Sources: Wikipedia, Wikidata.· Stadtwerke Köln on Wikipedia· Logo: Stadtwerke Köln GmbH, Public domain · trademark. Photos from Wikimedia Commons.Logos come from Wikimedia Commons (a few are the icon from the company’s own website). Most are public domain as simple text or shapes, but they remain trademarks of their owners and are shown only to identify the maker or operator. All operators.
