The 1800 seat Guangzhou Opera House designed by Zaha Hadid Architects opened formally in February 2011. The design of the interior of the performance hall was completed with input from Marshall Day Acoustics (MDA). This paper follows the design process for the Opera House interior from the discussions of the initial design concepts and the development of design parameters for the room, to the creation and modelling of the principal reflection surfaces. The process of modelling in Odeon and with a physical 1:10 scale model is described. Inclusion of diffraction surfaces sympathetic to the design of the venue was achieved. Measured parameters from the commissioning tests are presented.