Traditionally, visualization systems were tailored for specific work situation. Researchers have been trying to solve usability problems. However in public settings, visualization systems have to be entertaining enough for the user to interact with them. We designed, developed and evaluated a system called JatsiTatsi for the visitors to visualize information related to a large public entertainment event, the Pori Jazz Festival. To address the requirement of playfulness, we proposed an interaction techniques drawing from the analogy with a ball pool and balloons. Our contribution is an interface that takes into account a new dimension in the design of information visualization system: the fun users have with interaction, in addition to usefulness and usability.