The amphitheatre lies in the south-western part of Terni and is the only Roman monument still largely preserved and open to visitors.
Due to its constructive characteristics it can be dated to the first century A.D., before the building of the Coliseum in Rome. For a long time the amphitheatre was attributed to the construction work of Fausto Tizio Liberale, mentioned on a large slab, erroneously interpreted as being a dedication of the amphitheatre itself.
Its overall dimensions are 96.5 by 73 m, with an average capacity of approximately 10,000 spectators.
A part of the building still retains the original walls, while the rest can be easily constructed due to the perfect superimposition of the subsequent Medieval and more recent phases, which were built directly on the ancient monument thus respecting the original plan.
In fact, the amphitheatre today can be found near the 17th century Carmine Church, the Passeggiata public gardens and the Duomo. The monument must have appeared extremely animated and pleasing, thanks to the choice of a reticulated masonry, made using blocks of two different colours and framed by pilasters.
It was embellished by a succession of arches, most of which closed, with the four main entrances at the ends of the two axes.