Air conditioning system is an indispensable part of buildings today. The cost of this system increases with the rise in energy consumption which poses a challenge as well as air distribution in large auditoria. Analysis of results can also be daunting when designing this system. The study focuses on designing an air conditioning system in a large auditorium, applying Computational Fluid Dynamics (CFD) and visualizing the result in a Virtual Reality (VR) environment. The 3-dimensional model of the 520-capacity Technology Lecture Theatre, University of Ibadan, Nigeria was drawn with Autodesk Revit and modified into the geometry applicable for Displacement Ventilation (DV) and Mixed Ventilation (MV) for ease of numerical analysis with ANSYS Fluent. The building model and simulation results were then imported into Unity software for visualization in VR. The DV achieved better thermal comfort and air distribution in the computer simulation. At a supply temperature of 292.15 K, the DV system was able to keep the auditorium temperature at about 296.50 K, while the MV system at a supply temperature of 289.15 K was only able to maintain the temperature at 295.40 K. The temperature profile showed that the lower region where the students were seated was colder in DV compared to MV by at least 3 K. The results were also observed from a convenient position in VR. This study, with the aid of CFD and VR, was able to establish that displacement ventilation design has better air flow, lower energy consumption and is efficient for an air conditioning system in a large auditorium.