This paper presents the design of an interaction environment for fostering social interactions in electronic marketplaces. The environment incorporates a novel, spatially-organized, and interactive site map. The map provides visibility of people, activities, and social interactions and incorporates mechanisms for social interacour design constraints abstracted from prior findings in CSCW guided the development of the map: sociality, scalability, spatiality, and imageability. The design evolved through a process consisting of several phases and iterations. We used HCI techniques, where appropriate, to analyze and study the design problem, to enumerate, explore, and reconcile a design space, and to informally evaluate a design solution. Keywords Activities, crowds, e-commerce, imageability, interaction design, map, people, online communities, scalability, social groups, social interaction, social navigation, social visualization, sociality, and spatiality.