This paper deals with the calibration of structural models and soil for assessing the seismic vulnerability of 20th-century concrete heritage structures. The research focuses on a case-study heritage building, the Ledra Palace Hotel in Nicosia, Cyprus. Situated in the buffer zone dividing the city since the 1960s, the hotel consists of 4- and 5-storey massive structures separated by seismic joints. This study involved calibrating the structural model of one section of the building, using a seismometer (TROMINO) to record modal characteristics and to determine the soil profile underneath. A detailed methodology for calibrating the structural model in SAP 2000 is hereby described, aiming to align the measured fundamental period and mode shape with the modal analysis equivalents. Additionally, ground measurements helped create the soil profile and identify the ground type to define the seismic spectral demand. The aforementioned approach for non-destructive data collection for building model calibration is vital for assessing the seismic capacity of heritage buildings, as extensive destructive tests or alterations during retrofit may result in loss of heritage values.