Corso Mazzini (and beyond). This is the last tract of the National Cross-Road mentioned above. It is the main artery of the historical centre and the Corso par excellence. It is also the most modern and is flanked by beautiful buildings. In contrast, it leads off to decidedly mediaeval streets and lanes. After the Seat of the Tribunal Courts (formerly the convent of the Filippini) there lies via Plinio il Giovane on the left. This is the continuation of Piazza del Mercato and is also of Roman origin. By going down this street, one comes across piazza Sordini with Sala Pegasus (formerly the twelfth-century church of St. Laurence).

On the uppper side there is Palazzo Rosari-Spada (17th-18th century, but with the façade left unfinished). The other palazzo houses the Ente Teatro Lirico Sperimentale "A. Belli". At the bottom of the steps Piazza Collicola opens out. The name derives from the eighteenth-century building situated here which is now the Municipal Gallery of Modern Art. On the other side the square and the church of San Domenico. After via Plinio il Giovane on the Corso, to the right, the back entrance to the Galleria d'Arte Moderna can be found together with the picturesque vicolo dello Sdrucciolois a steep climb of steps underneath lovely arches leading to piazza della Genga and piazza del Mercato.

At the back and to the right, underneath a wide vault, there begins a street with a small portico in stone The Portico di Sant'Agata of the church of Sant'Agata probably dates back to before the year one thousand. Its nave houses thirteenth-century frescoes whereas the apse has been re-built and is part of the back drop of the Roman theatre behind it.

To the left of the church one can find the mediaeval Palazzo Corvi and the entrance to the National Archeological Museum. By going further along and down the street, one can reach the Borgo di San Matteo otherwise called "Il Borgaccio" whose main street is via Mameli. this street begins at the intersection of via di Sant'Agata, via vittori (from Piazza Collicola) and via delle Monterozze (from viale Matteotti and open to traffic). On the right of via Mameli there are the ruins of the former church and monastery of St. Matthew. Porta San Matteo was built in 1296, together with a long section of the walls to the left, to close off and protect this Borgo. The gate is also called "di Loreto" because of the church facing it.

In front, the Portico leading up to the beautiful sixteenth-century church of Madonna di Loreto next to the civil hospital "San Matteo degli Infermi"