A common characteristic of religious spaces in Eastern and Western Mediterranean cultures is the existence of large curved surfaces, usually in form of domes at the ceiling. Modeling of such spaces using geometrical acoustic algorithms typically requires discretisation of curved surfaces into planar elements. The degree of discretisation plays a crucial role in the quality of results, and simulation of several acoustic phenomena such as focusing. In this paper an investigation of the size of discretized elements is performed using the ODEON Room Acoustics Software, version 13. For this investigation a model of the mosque “Selimiye” has been used. Impulse responses of this space were recorded in many positions as part of the CAHRISMA project (Conservation of Acoustical Heritage by the Revival and Identification of the Sinan’s Mosques Acoustics) in 2000–2003. The model has a big central dome and several other surrounding curved surfaces. Measured room acoustic parameters are compared with simulated ones while varying the discretisation of curved surfaces and several simulation parameters for the best possible agreement. The advantages and disadvantages of very high discretisation are discussed, and the question whether there is an optimum degree of discretisation or not is addressed.