Most of ancient Rome was settled on the Tiber River Holocene flood plain. Monuments of Imperial age (I to V century) show evidence of significant damage, mainly produced by earthquakes generated in the seismogenic areas of the Central Apennines, 70 to 130 km away from Rome. The different level of damage suffered by the two most important honorary columns in Rome, those of Trajan and Marcus Aurelius, located 700 m apart, suggests the occurrence of strong variations of ground motion across a narrow zone due to changes in the local geology. In order to check this hypothesis, we investigate the details of surface and subsurface geology of the area. We construct a 2D geological profile which includes topographic variations and heterogeneities of the elastic and anelastic parameters. A finite-difference technique is used to compute the SH-wave response along the profile. Numerical modeling of seismic response at the site of Marcus Aurelius' column shows a significant spectral amplification in a narrow frequency band corresponding to the natural vibrational mode of the column. The amplification attains much lower values at the Trajan's column site.