The walls are formed of large blocks of limestone and they are still rough, unlike the others in the area. The part of the walls that is most scenic and interesting to visitors is the second outermost circle, which dates back to the 4th - 3rd century BC, built as a result of the considerable urban expansion and the threat of Rome. It extendd on either side of the central Porta Romana for about 800 meters and consists of megalithic blocks called polygonal because of their irregular geometric shapes. At the top, and in other sections of the wall, work dates to late Roman and medieval periods.
This masonry is certainly less interesting than the pre-Roman, even though it helps to give continuity to the development of the imposing defensive Amelia perimeter unique in its kind. One of the original entrances to the city walls, is very interesting; the so-called Gate of the Sun, it is raised above street level on the north-east side of town. European travelers of the 18th century were impressed by the mass of the blocks and the imposing walls, said that they were the work of a legendary people, the Pelasgians.