Düsseldorf is the capital and second largest city in the German state of North Rhine-Westphalia, and the seventh largest city in all of Germany. Yesterday, Düsseldorf's mayor presented the above mark that will be used to market and represent the city. Reports say it will be supplementary and that existing city logos will remain in use.
The new symbol is recognised around the world as a happy emoticon, that is produced a colon and the letter D. That letter also happens to be the first letter in Düsseldorf. It was created by BBDO who were selected out of 66 agencies, five of which where allowed to put forth proposals to the mayor.
Update December 2: For more on this project I'd recommend Design Tagebuch, where you'll find much more information (in German) and plenty of images.
--- Comment Designink.nl ---
The original post also mentions 2 similar marques by commenters (Dubrovnik and Denmark).
Other interesting links i found on the subject of 'emoticons';
University of the Arts London by Pentagram
Skype; create your own humoticon;
Onderzoek emoticons I
Onderzoek emoticons II