This paper resumes some experiences in the field of the experimental dynamic characterization of historical buildings made by ENEA in the last decades. Indeed, traffic-induced vibrations could be very dangerous for ancient buildings even in the case of low-level vibration amplitude, due to the long-time exposure of the constructions to these cyclic loads. Thus, experimental dynamic methodologies allow us to define the dynamic behavior of the structure and will permit damage evaluation by monitoring the changes in dynamic properties. The role of the underground conditions on the dynamic response of the monuments is also highlighted in the case of the Lateran Obelisk.