The Gargarasi Castle, today "Residenza Antica Flaminia", was erected on the edge of a precipice which towers over the Treia river valley, a short distance from the confluence with the Tiber river, in the land of Civita Castellana.
In past centuries its position was of unsurpassed strategic value, ensuring total visual contact with the city and control of both the Valley road as well as the Consular Flaminia Road.
The Castle is located exactly where a majestic viaduct dating back to Roman times and known as the Wall of Sin, ensured the continuation of the Flaminia despite a drop of almost 50 metres which separates the Treia valley from the tuffaceous plane above.
It has been identified as dating back to Medieval times in virtue of its conformation.
Although modest in size, the walls are characterised by the presence of a large entrance arch, under which the Flaminia Road passed.
The arch structure is clearly visible in a nineteenth century photo, as well as the ruins of what appears to be a Medieval construction which has since disappeared.
The route of the Flaminia road was definitively changed in the early seventeenth century, during the pontificate of Paul V. The original stretch dating back to Roman times was permanently excluded from the main road network.
The old route is easily recognisable, with numerous occhialina basoli (leucitic stone) emerging from the ground.
In the park of Residenza Antica Flaminia, towards the castle, the clear cut tuffaceous quarry is clearly visible, dating back to Roman times. It was used for support works along the consular road, the most important of which was the aforementioned Wall of Sin.
During a later period, a two-storey abode was excavated (which can still be visited today), similar to the most renowned examples of hermit caves dating back to the Early Medieval Ages, widespread throughout Roman Tuscia.