Stadium Australia is to be the centrepiece of the year 2000 Sydney Olympics. The architects aimed to minimise energy consumption by incorporating passive design measures which would provide ventilation, natural cooling and warming and daylight. This paper describes the simulations undertaken to guide the design of one space in the stadium - a banquet hall. Lighting simulations demonstrated that a facade design incorporating external fixed, horizontal shading and a light shelf can provide satisfactory daylighting levels and permit winter solar gains to offset heating demands, whilst excluding the summer sun. Thermal analyses illustrated that natural stackdriven displacement ventilation can deliver conditions which might be considered comfortable despite the hot, sunny summer-time conditions. The strategy employed ground cooling during the day, and night venting to cool insulated thermal mass at night. Summer comfort cooling could easily be incorporated to guarantee satisfactory internal temperatures. This hybrid solution had much lower energy demands, plant loads and operating periods than a conventional air-conditioned solution. Computational Fluid Dynamics (CFD) analyses demonstrated that sufficient fresh air could be well distributed throughout the hall and that night venting would occur. State-of-the-art simulation enables innovative, low energy design solutions to be pursued by architects and clients with greater confidence. It will continue to play a vital role in the environmental design of the world’s largest and most prestigious buildings.