Founded possibly as early as the 7th century BCE, Ostia Antica truly began its significant development around the 4th century BCE as Rome's first colony and military outpost. Its strategic location at the mouth of the Tiber River made it vital for Rome's naval defense and, crucially, for its food supply. As Rome expanded, so did Ostia, transitioning from a military base to a bustling commercial port. By the Imperial era, particularly under emperors like Claudius and Trajan, Ostia flourished, undergoing extensive urban development. It became a vibrant cosmopolitan city, home to warehouses, commercial offices, public baths, temples, a theatre, and multi-story apartment buildings known as 'insulae'. Its peak prosperity lasted until the 3rd century CE. With the decline of the Roman Empire, changes in the Tiber's course, and the rise of new ports, Ostia gradually lost its importance. By the 9th century, it was largely abandoned, its structures slowly covered by silt and vegetation, which ironically contributed to its remarkable preservation until systematic excavations began in the 19th century.