Ostia was the port city of ancient Rome. Once a thriving city of around 60,000 people, today it gives an excellent look into ancient lives with docks, warehouses, apartments and mansions, shops, baths and temples. Founded around 600 BC as a source for salt to preserve meats, it was conquered by Rome in around 400 BC in order to become the city's fortress and port at the mouth of the Tiber River.
As Rome expanded, it needed a bigger port so Ostia was abandoned. When the Roman Empire fell, Ostia became a ghost town - even the river moved away over time and Ostia became buried under river mud. This is what preserved it and leads some to now compare its preservation to that of Pompeii.