the 3rd century in the reign of Alexander Severus (222-235), Maximinus Thrax (235-238), Philip the Arab (244-249). The construction of the Roman Amphitheatre of Albano Laziale can be dated to the middle of this century and could mark the end of the period of highest prosperity for the Legio II Parthica although it may no longer have been there. Decline of the castra after Constantine Legio II Parthica is mentioned for the last time at the beginning of the 5th century, near the camp of Cepha (modern Hasankeyf, Turkey). Thereafter it disappears from history. But even at the beginning of the 4th century, the legion had abandoned Castra Albana to settle in the strategic city of Bezabde (modern Cizre, Turkey) on the river Tigris, at the ever troubled eastern border of the Roman Empire. In the Liber Pontificalis it is stated that the Emperor Constantine I (306-337) founded the Cathedral of San Giovanni Battista at Albano Laziale during the pontificate of Pope Silvester I (314-335), providing the cathedral with decorations and substantial property in the Alban Hills, including the sceneca deserta vel domos civitatis (the abandoned tents or the houses of the city). It can thus be deduced that modern Albano Laziale was born on the remains of the castra, which explains the fact that the historic centre of Albano Laziale is literally founded atop the ancient encampment, whose remains are generally found only 50-200 centimetres below the modern ground level. Description Archaeological remains Circuit wall Like all Roman castra, the Castra Albana followed a strict civic design, forming a large fortified rectangle with four gates (praetoria, decumana, principalis sinistra and principalis dextra), with rounded corners reinforced by circular turrets (an unusual feature, but similar to the castra of Hadrian's Wall in Britain). The construction technique is Opus quadratum - one of its latest appearances in the Ager Romanus (it was supplanted by Opus latericium). The construction material is Peperino, extracted in situ from the volcanic soil on which the castra was built, which would have saved time and money. The construction was made difficult by the position of the encampment on an 11 degree slope, a situation which required a technical solution - a differing placement of blocks depending on the slope at different points on the wall. The perimeter of the wall circuit is 1334 metres; the northwest side measures 434 metres, while the parallel southeast side measures