- a sign of the contraction of the inhabited area at the time. It has also been possible to identify the location of another street within the castra: the via quintana (Fifth Street), which connected the rectangular guard towers. Given the location of one of these towers in Castro Partico Street, the remains of a perpendicular street were found on the part of the via principalis in San Francesco d'Asisi Street, a little past Liceo classico statale Ugo Foscolo. Pretty abundant remains of the circumductio, the street which encircled the walls on the outside, and of the intervallum, the street which ran around the inside of the walls. With respect to the circumductio, portions have been discovered along the north east side under the modern Tacito Street; along the southwest side near the aforementioned rectangular guard tower on Castro Partico Street, 1.5 metres below ground level at a spot 18 metres from the porta principalis sinistra, and a little further along in the public carpark; along the southeast side 0.5 metres below San Pancrazio Street; and along the northwest side in the piazza della Rotonda, on San Gaspare del Bufalo Street and in the piazza San Paolo. A terrace from the intervallum remains on the northeast side, as well as a good stretch near the porta praetoria and at the end of Aurelio Saffi Street on the southeast side, and also some bits on the northwest side. Outside the castra, under the modern Giacomo Matteotti Road, many remains of the foundations of the Appian Way have been found. There are also some remains at the end of Risorgimento Ave and Europe Ave. The porta praetoria is six metres above the Appian Way and twenty metres away from it. It is unknown how this gap was bridged - presumably there was a stairway for pedestrians as well as one or two paths for vehicular traffic which descended from the gate to the regina viarum (Queen of Roads). Part of such a stairway, running in a north–south direction, was thought to have been discovered in the 1980s under Palazzo Savelli, during the construction of public toilets. Internal buildings The "Round Building" The "Round Building", today known as the Santa Maria della Rotonda is the best preserved Roman structure in Albano. The circular interior has a circumference of 49.10 metres and mimicks the Pantheon in Rome on a reduced scale. However, the building