The paper describes the state-of-the-art of room acoustic auralization and the results of two different ways to validate the quality. The first method is an objective measurement of room acoustic parameters from the simulated impulse response using a monaural auralization filter. The measurement results are compared to the calculation results from the simulation. The other method is a subjective comparison by listening to three different binaural reproductions: The computer simulation, the recording with a dummy head in the real room, and a convolution of the measured binaural impulse response with an anechoic recording. This comparison has been made as part of a large project on Byzantine churches and Sinan’s mosques in Istanbul