In this paper we discuss how an interaction design perspective on the design of interactive artefacts in public spaces can encourage us to explore certain issues concerning the inclusion of visitor input into our installations. We see the role of technology as supporting people's experiences of heritage-moving away from simple delivery of information towards enabling visitors to add to the content of the exhibition. This approach encourages active reflection, discussion and appropriation in the tradition of best practice in human-centred interaction (HCI) design. In this paper we discuss two exhibitions/installations in which we have been involved, Re-Tracing the Past and The Shannon Portal. The former was developed with the objective of engaging visitors and enhancing their overall experience of a personal museum collection; the latter had the goal of encouraging visitors and travellers to share their experience of Ireland. We then discuss the impact of this design strategy and analyse the role of visitors' contributions to each exhibit, and the particular interactions between participants and the content they produced.