**1. Introduction**

Very often, the instability of sites and artificial structures is attributable to human activities and to interventions carried out without special preliminary geotechnical studies. The most common procedure for assessing unstable sites includes base studies such as drilling boreholes, shallow excavations, and engineering geology studies. More and more often, some geophysical surveys are associated to the above intervention, represent the first phase of assessment, and allow optimizing the possible campaign of excavations and boreholes. The geophysical methods provide extensive and continuous information (usually along sections not necessarily vertical), are moderately invasive, and are convenient from an economic point of view. Two assessment examples of unstable sites are illustrated here. The first case concerns the ancient walls of an Italian city, and the second case concerns a slope on which develops a road.
