A new excavation began as part of the research in the northern part of the territory of Velletri and with the aim of checking in the field new important data regarding occupation between the mid Bronze to late medieval period in the area of Mount Artemisio which emerged during a survey begun in the mid 1990s. The project is the result of collaboration between the Archaeological Superintendency for Lazio. The University of Rome “La Sapienza”, the municipality of Velletri and the Castelli Romani Regional Park. To date research, which is still in progress, has been conducted in the central and highest part of the Artemisio massif and at the northern limit of the area involved, in the locality of Colle del Vescovo, and on the Maschio d’Ariano. The excavations were undertaken by Mr. Carlo Brecciaroli, of Ecol B, with the scientific direction of Dr. Luciana Drago and field direction of Dr Manuela Merlo and Dr. Silvia Ten Kortenaar (Colle del Vescovo and on the summit of Mt. Artemisio), Manuela Merlo and Paolo Dalmiglio (Maschio d’Ariano) with the assistance of Dr. Gina Trombetta. The project was financed in the first phase (1999-2002) by the municipality of Velletri, on the initiative of Anna Germano director of the Civic Museum, and more recently (from 2004) by the Castelli Romani Regional Park. It is part of the activity of the Etruscan and Italic Antiquities section of the Department of Sciences of the History, Archaeology and Anthropology of Antiquity, University of Rome “La Sapienza”. On the summit of the Maschio d’Ariano, in an area (part of the territory of Lariano) where, after the 11th century, numerous semi-hypogean dwellings and defensive structures were built, an excavation began in July 2004 financed by the Castelli Romani Regional Park. This investigation clarified the preliminary results of the historical-topographical research undertaken by Gina Trombetta regarding the medieval castle of Lariano and the survey data regarding the site’s earliest occupation phase. The trench was opened on a terrace at 870 m a.s.l. immediately south-west of the Maschio’s summit (891 m), up against a substantial defensive wall/and or terrace wall which the stratigraphy dated to the 11th-12th century. The medieval layers produced the remains of a lime kiln and several pits, including one for grain storage, suggesting that this was a production area prior to the construction of the wall. Below these layers were the remains of a cobbled surface datable, on the basis of the associated finds, to the early-mid Republican period, which continued in use until at least the early Imperial age. A building with phase I tiles, in use between the 6th-5th century B.C., also came to light. Amongst the pottery fragments found within the collapse of the archaic building was a red-brown impasto foot with a letter X incised on the interior. The large amount of residual brown impasto pottery in the several layers documented attested an earlier occupation of the site dating to the late Bronze Age and the Iron Age.