The Ducal Palace of Camerino (Italy), a renaissance monumental building, was severely damaged by the Central Italy earthquakes in 2016 and currently interventions are being planned for its structural restoration. Given its very complex structural behaviour and the need to calibrate numerical models able to predict its seismic response with adequate accuracy, one of the most iconic and critical portions of the Ducal Palace, i.e., the quadriporticus Portico Varano,  was equipped with a long-term monitoring system, characterized with different types of sensors, accelerometers, linear potentiometric transducers, temperature and relative humidity sensors, and weather station, to achieve a complete measure of the structural behaviour and relevant environmental conditions. The long-term monitoring and related field activities, that also included non-destructive inspections and testing of materials, are part of a wider study on strategies for saving cultural heritage foreseen within a recent European research project named ARCH. In this paper, the dynamic characterization of the Portico Varano is discussed, showing the optimization of sensor positions subsequently the preliminary installation. It is shown that the monitoring system provided data essential to support decisions involving the design of interventions finalized to preservation of such an architecture heritage to the future generations.