The area described in this article was ‘detected’ by the Laboratory for Landscape Archeology and Remote Sensing, University of Siena research team during aerial prospection in spring 2005. Analysis of the aerial photographs allowed interpretation of the site as a triple-ditched enclosure. During subsequent field-walking survey a number of archaeological artefacts were collected and mapped. Differential global positioning system (DGPS) survey confirmed the morphological pattern of the site, which seems to represent a survival of the Early Medieval Age settlement pattern on the coastal plain. The field-walking and DGPS surveys were followed by a programme of geophysical survey combining three different methods: differential magnetics (Overhauser probe), ground-penetrating radar (GPR) and Automatic Resistivity Profiler (ARP©, Geocarta). Finally, three sample areas were excavated, mainly to test the evidence collected previously. The excavation data – ditches, post-holes, domestic pottery, animal bones, and wall remains – support the interpretation of the site as the first earth-and-timber castle mound, or motte, to be identified in Tuscany.