This paper focuses on the dynamic characterization approach to evaluate the conservation state of carbonate building stones of monumental structures. In particular, we report the use of elastic waves at an ultrasonic frequency of 54 kHz to define quantitatively some dynamic properties of carbonate rock types used as building materials. Measurements of compressional and shear wave velocities have been carried out and the relationship between some physical properties of the investigated rocks and these geophysical measurements have been evaluated. The ultrasonic data were also supplemented by a petrographical study of these rocks to correlate their petrophysical features with the elastic ones. Based on the results of the laboratory measurements, in situ applications on a significant monumental structure have been also carried out to check zones of weakness and to assess the state of deterioration of the investigated stones. A comparison of laboratory and in situ results confirms that dynamic characterization is a useful approach.