One of the most important and beautiful Umbrian archaeological sites is the one in the area of Carsulae, between the municipalities of Sangemini, Terni and Acquasparta (Tr) at the foot of the Martani Mountains. The city was erected after the opening of Via Flaminia, which represented a moment of great development, turning it into one of the “stationes” of the road itself near the springs of San Gemini and a point of reference for the surrounding populations. Carsulae was a rich city, an outstanding cultural and civilisation centre; yet it was abandoned by the inhabitants that moved to the hillsides (probably Cesi) from which they had arrived several years before. The cause for the decline of the Roman city is not clear; it is thought that the main cause may be identified in the replacement of the old course of Via Flaminia with the new Eastern section of Terni - Spoleto, although the possibility of barbarian invasions or of an earthquake is not excluded. The ruins of this city were discovered in the XVI century, when Prince Federico Cesi begun the first researches in the territory. However, only the excavations between 1951 and 1972 unveiled a large quantity of substantially undamaged monuments and structures.

The itinerary to visit the archaeological area begins from the Church of St. Damian, a medieval building erected on the ruins of a Roman building, some traces of which are still visible nowadays. A small portico with two colonnades were added in the front side. Particularly interesting before the church is the paving of Via Flaminia which has remained mainly intact. More southward there are the ruins of a spa complex, where the tanks of the water conservation system are still visible. Continuing the visit, it is possible to admire the forum, the square of the city where public activities were carried out, endowed with two arches that allowed its access. Around the forum there were some public buildings. Two small identical buildings – the twin temples – were erected on the southern substructions; they were devoted to a couple of gods, and only the two podiums in pink stone remain. Before the forum, there is a great Basilica, where commercial and administrative activities were carried out. The external appearance was marked by a covering of marble plates, some remains of which are still visible, whereas the internal area is divided into three naves, two rows of pillars supporting the covering and a semicircular apse at the back.

On the eastern side, there is the imposing complex of the amphitheatre and the theatre. The former was erected through a natural hollow that allowed to construct the stairs from it, whereas the theatre was completely erected on the ground. Through Via Flaminia, it is possible to reach the Arch of St. Damian, a monumental city gate; by exiting it, the monumental necropolis is visible, a funerary building of great architectural value. .