At the mouth of the Tiber river lies Ostia, Rome’s port town. Legend has it that Ostia was founded as Rome’s first citizen colony (a colonia civium Romanorum) back in the 600s BC, but the archaeological evidence dates the first structured settlement, which was protected by a wall of tufa blocks, to the 300s BC.1

Soon the settlement outgrew the small castrum (as the area surrounded by the early wall is called today) and both private and public buildings spread out in every direction. The Roman Late Republic (c. 133–31 BC) brought hardship on several occasions. During the first four decades of the last century BC, the inhabitants of Ostia suffered both from troops involved in civil warfare and from a raid by daring pirates from the eastern Mediterranean.2 The town was unable to protect itself adequately, since it lacked a proper town wall.