Postcard with map on one side, rules on the other including goal, set up and gameplay. The card substitutes instead of a building card from base game. You use teh Microville card instead the regular/challenge building. You have to prepare the 4-card city as usual and put Microville next to it. You don't go to Microville with your Engineer, you build Microville with your regular build action. You score points for what you've built and for the sets of 3.