Pervasive games are staged in reality and their main attractiveness is generated by using reality as a resource in the game. Yet, most pervasive games that use mobile and location-based technology use reality only in a weak sense, as the location for a computerized game. In this article we analyze two game practices, Nordic style live action role-playing (larp) and alternate reality games (ARG), that instead use reality as their main game resource. We analyze how they go about creating a believable game world and encourage the players to actively take part in this world. We present two example games that do the same with the support of technology, effectively realizing an immersive game world through a combination of physical play and technology-supported play.