Structural control monitoring (SCM) is essential to assessing the state of conservation of strategic constructions, especially the historical ones. Non-destructive (ND) tests based on Ambient vibration measurements can be efficiently implemented with numerical tools to describe the structural performance of the buildings. The uncertainties related to the masonry behaviour and the presence of any damage are current problems that could be solved by the Operational Modal Analysis (OMA) approach proposed. In this paper the results of an experimental survey through specific sensors (tromograph, velocimenters) which transform ambient vibrations in term of sensitive information, from a engineering structural point of view. Frequency peak, resonance frequency and mode shapes are obtained to characterize the location of the Department of Architecture and Design of IUAV University. The former convent was restored by Iuav University in the late 1990s with renovations and architectural adaptations that maintained the formal, distributive and structural features typical of a seventeenth-century convent. The recordings are performed closer to the structural interventions to highlight possible correlations. In addition, a deterministic approach for Optimal Sensors Placement (OSP) is employed in order to identify how properly place the accelerometers to maximize the quality of SHM information with the minimum number of sensors, aiming to validate the effectiveness of future applied strengthening solutions.