If that title didn't make your brain explode, then your obviously too young. It's true, at this very moment there is 3 seasons planned of 26 episodes each! HOLY SHIT! That means potentially 3 (or more) cities to discover.
Follow the link for news and SCREEN SHOTS!!!!
http://www.catsuka.com/news/2012-05-17/les-mysterieuses-cites-d-or-2-premieres-images-diffusion-prochaine-sur-tf1