About a quarter of a mile farther south, near the Latin road, there is an outlying building which seems to have been intended to command a view of that road. The railway to Frascati now runs between the Claudian aqueduct and these ruins. The castella of the Aqua Marcia, the Tepula, the Julia, the Claudia, the Anio Vetus, and the Anio Nova lie on the right of the old Latin road here, at the sixth milestone, where the arcades make a right angle. The old road then runs to the right of the present road to Frascati, nearly on the line of the modern Strada di Grotta Ferrata, and ascending the slopes of the Alban Hills, passes behind Tusculum and Corbio, along the valley called Vallis Albana. [Sidenote: Tusculum.] Since the excavations carried out by Lucien Bonaparte at the beginning of this century, there has been no doubt left as to the site of the ancient city of Tusculum. The ruins lie from about a mile and a half to two miles above Frascati, upon the ridge forming the edge of the most ancient crater of the Alban Hills. Between this ridge, which bore the name of Tusculani Colles, and the hills upon which Marino and Rocca di Papa stand, the great Latin road ran. Tusculum stands just over this road and was approached from it by a steep path ascending the northern side of the valley. The main road entered the city on the other side, from the direction of Frascati and Rufinella, leaving the Via Latina at the tenth milestone, between Morena and Ciampino. The ancient pavement of this road can be clearly traced on the slope of the hill above Frascati, and it leads us along the top of the hill through what has plainly been the main street of the town to the citadel, which stood at the eastern extremity. [Sidenote: Theatre.]