The characteristics of a performing arts space have a great influence on the experience that both artists and audiences have during a show. Therefore, it is of great importance to understand the sound field behaviour, the lighting, and the thermo-hygrometry of the ambient conditions existing inside this cultural heritage. The aim of this paper is the presentation of a complete assessment in relation to the comfort of an Opera theatre on its whole. As such, it has been undertaken a study in relation to the acoustic listening situations other than to the parameters related to the light level and temperature comfort of the Valli Theatre of Reggio Emilia. The acoustic characterization has been undertaken in line with the ISO 3382 standard measurements procedure by capturing the room impulse response (RIR), while the light intensity has been studied by using the lux meter. In addition, the thermo-hygrometer has been used to photograph the comfort related to temperature and relative humidity inside the main hall.