For now, City Tours doesn't offer too many interesting features: it only lists popular sights and it suggests when you should visit them. You can edit the information about a place and you can add new sights, but the options are very limited.
It would be useful to show more details about sights from Wikipedia and from image hosting sites like Flickr or Panoramio. Google works on landmark recognition, a project that associates images from the web with landmarks, and City Tours is an obvious application.
{ Thanks, Dan. }