: Computer games play an increasing role in our modern information society. Besides pure entertainment, games can provide valuable input for social interaction, learning, etc. Recently, new pervasive game genres have been developed, including mobile games, tangible games, table-top games, exhaustive games, mixed reality games, etc. Pervasive games extend the traditional game experience by supporting natural contexts within game experiences. In this paper we present ECHOES as a new mobile pervasive multi-player game which is played outside the boundaries of a building. ECHOES combines the classic features of hunting games with the logic of riddles to create a fun and exhaustive experience in a city.