In the context of a PhD thesis, in which the main purpose is to analyse the importance of the public square/place (“agora”) as a meeting point of sound and music, with particular regard to its use for concerts (amplified or not), a first step was done, making comparisons between measurement in situ and results coming from a computer simulation program (Odeon), usually used for enclosed places, such as theatres, concert halls, etc. The main objective of this paper is to study how accurate such a program is for analysis of this kind of open spaces, which could have a regular or a complex shape, and which is not completely closed and not completely open, with highly reflecting and partially diffusing vertical surfaces (the facades) and with one totally absorbing surface (the sky). A natural application of these results will be the possibility to detect the best position for a sound source (typically an orchestra or a band during, for instance, music summer festivals) and the best position for the audience. A further result could be to propose some acoustic adjustments to achieve better acoustic quality by considering the acoustic parameters which are typically used for concert halls and opera houses.