ARCHIE is a research project in which the educational staff of the Gallo-Roman Museum collaborates with the Human-Computer Interaction research group of the Expertise Centre for Digital Media (Hasselt University) in the context of the expansion of the museum. The starting point of this interdisciplinary collaboration is our strong belief that handheld guides are a promising medium to enhance visitorsí learning experiences in a museum and strengthen the experience of a group visit. In this paper we present a first application: a collaborative trading game for (school)groups of children; from conceptual stage towards final implementation and conclude with user test results. We designed the museum game so that every player is dependent on the concrete actions of other players; only through social interaction and cooperation can they come to a good result.