We discuss the use of multiple design representations to enhance decision making at the early stages of design. Our interest is how the context in which design decisions are made can be extended by two interrelated approaches: (1) the incorporation of the temporal, (2) through the concurrent evaluation of qualitative representations and quantitative information. Outcomes from a practice survey and observations from design studios are used to inform the development of mixed reality (MixR) technology, to enable the applications to reflect architecture specific modes of design praxis. We propose two approaches - studio MixR and site MixR - reflecting the distinction between typical studio based design process and the requirements of a formal design review by the design team and stakeholders. Prototype applications have been implemented and a number of projects have been undertaken to illustrate some of the potential of mixed reality for architecture and urban design. These focus on the early stages of design, from the abstraction of parametric design to on site design reviews undertaken with augmented reality visualization.