The toponym Castello Antico indicates, in the cartography and in the oral tradition, an irregularly elliptical screw, located south-west of Lemprato, in the municipality of Idro. The summit is flat, but with two distinct plains, at slightly different altitudes. In 1980 in the locality of Castel Antico excavations were carried out, whose findings attest the existence of a village of Roman age probably dating back to the first century B.C. The territory of Lake Idro was inhabited, at the time of the Roman conquest, by the tribe of Edrani, attested in an epigraph preserved in the parish church of Idro. The vast majority of the finds consist of ceramics. Among them, the most prominent are the raw ceramics, among which we find types that seem characteristic of the so-called Rhaetian area. Next to the materials, of extreme interest are the buildings identified. From the general plan is first of all highlighted the same orientation of the buildings: this may suggest an organized urban system or at least an orderly development of the country. The excavation of the town of Castello Antico provided valuable information on the cultural and material transformations induced by the Roman conquest of the Alpine valleys, in particular with regard to artifacts and settlement structures. Lemprato and Crone are the hamlets with an older origin. The village of Lemprato is characterized by the presence of complex residential structures of a palace character. This fraction differs from the others because the church, generally a central reference point, is moved to the end of the town. Even the undeveloped central space consists not in a typical square, but in an area used as a public park. The nucleus is also divided into two villages: the lower and the upper, called Castle, having a very unitary appearance, which in some way recalls the centers of lordly origin, where the residential function of the buildings was combined with a function of representation and prestige linked to a certain social level. It perhaps also had a defensive control function, given the position and a certain closure of the town, which suggests a sort of walled village with one or perhaps two access doors. The lower part is very different, consisting of a series of smaller houses, although massive, located between the lake and the road.