The French railway company Thalys recently launched an entertaining advertising campaign via billboards in Paris, Brussels and Amsterdam. Each of the project freestanding billboards has a map of one of another trio city with 1,000 built-in audio jack ports. Passers-by just plug-in their headphones and hear random sounds from a neighborhood or tourist site from the other city. Of course the object of the campaign is to encourage the purchase of Thalys train tickets, but it’s a fun concept.