This paper explores issues of social context and interaction between digital and physical museum visitors, using as a focus of discussion the "City" project, itself set within a larger interdisciplinary project called "Equator." The paper looks at collaborative environments that span different media, in particular handheld mobile devices, Web-based hypermedia, and 3D virtual environments. Two main research strands are discussed: the methods and results of two pilot visitor studies in two cultural institutions in Glasgow (Scotland)--the Lighthouse and the House for an Art Lover--and the development of a prototype system that establishes three-sided collaboration between physical, Web, and virtual environment visitors. Preliminary results and issues arising from the on-going system development and user trials are then presented. Future plans for further system evaluation and deployment are addressed. (Contains 15 references.) (Author/MES)