We develop an interaction framework for huge public displays with multiple users in public spaces such as concourses, lobbies in buildings, and rendezvous spots. Based on this framework, we introduce an interactive system for public spaces called Mirai-Tube1. This system creates a scalable interactive media space and has a scalable real-time recognizer. A Mirai-Tube system was installed in the underground concourse of Minato Mirai Station in Yokohama. We conducted a demonstration experiment from 1st Feb. to 31st Oct. 2004. This trial represents the world's first experiment in a real public space in terms of its scale and its time period. We evaluate our interactive media system from three points of view: acceptability as a public media, how much attention the public pays to it, and its understandability as an advertising media. This paper describes the features, implementation, and operation of the interactive media system and the results of the evaluation.