In this paper we describe our current research in the field of interactive large public displays with mobile device interaction. The core of our research is based on a user interface concept that takes advantage of input and output capabilities of interactive large public displays and mobile devices. We call this concept the "dual display" concept, which allows us to execute multimedia user interfaces across both large and small display types. By shifting parts of a user interface down to a personal mobile device we argue that we can solve a number of problems originating from limitations in large display real estate. As a result of our research we have defined a number of design strategies focusing on the concepts of interactive dual displays. We also report on applying these design strategies to our development of large display applications, which we deployed and tested in lab environments as well as in public settings.