The ruins of the Roman city of Carsulae are located a short distance from Terni and the town of Sangemini, known for the presence of mineral water springs. The city was born along the Via Flaminia and as a function of it, as a center of aggregation of the pre-Roman populations residing on the hills and in the nearby countryside: the territory was in fact frequented in a very intense way already from the Middle Bronze Age, with settlements on strong positions, at the peak of reliefs that dominated the underlying plains and the natural communication routes. The opening of the Via Flaminia, traced between 220 and 219 BC, represented a moment of great development for the neighboring populations, who took it as a point of reference for the transformation and evolution of their way of life. The traffic that took place along the artery was a stimulus to the transfer of populations towards the areas it crossed; and it is in all probability in this phase that the center of Carsulae arose.

The choice of the site was dictated, as mentioned, by mainly economic reasons, linked to the presence of a major communication route along which trade took place between Rome and the Adriatic and more generally towards northern Italy; being on the edge of a fertile plain allowed profitable agriculture; the decline of Carsulae and its abandonment were on the other hand in direct relation with the loss of importance of the western branch of Flaminia, to the benefit of that for Interamna and Spoletium.

Of the republican urban planning phase, in the period coinciding with the opening of the road, there remain limited traces recovered in the excavation of the substructures of the temples of the forum. The definitive urban structure, however, dates back to the Augustan age, when the city obtained the municipal constitution and was assigned to the Clustumina tribe. The definitive decline of the place was determined - as well as by the movement of the main route of the Flaminia towards the Spoleto plain, and consequently by the abandonment of the "Carsula" branch - also by serious natural events, including a strong telluric movement which caused , among other things, the collapse of some sinkholes on which many public and private buildings were built and which made an already highly impoverished site inhospitable. Carsulae is not mentioned as an episcopal seat; the only Christian presence consists in the transformation of a Roman building into the church of San Damiano, home to a small convent of nuns.