Compare Ostia Antica to Pompeii - the one expiring over time as water levels altered and port capabilities diminished; the other with the drama of violence, painful death, sudden cataclysm.
Nonetheless, go to Ostia, near Rome, before your flight takes off. We stopped there on the way to the airport, in our rental car, but this article in New York Times 9/17/06 says at page 12 that you can take a boat there from Rome. Perfect. We squirrel away things like this for a return trip, and that is the great advantage of going first, researching later. Find what you want on a second run.
Less touristy, a sense of the place, the streets, the people. "Ostia" means mouth - and the city does seem to be swallowed - it ultimately melts away into the river. See the baths, amphitheater, storehouses, a synagogue, and a temple. Metropolis. Finally - as late as the 9th century, says the article, Ostia became a mere quarry area. Its marble went to Pisa, and Florence, anywhere needed. Organ transplants.
The communal nature of living in those days - we saw it also at the Roman villa in Sicily - see Sicily Road Ways , look for the Villa del Casale post. Hoppers were all in a square at the house, the holes looking at each other, with kindly running water beneath, all genders do your business and move on, group togetherness. Sometime look up the equivalent of TP, a stick with handy bulbous thing. Note also, as in Rome, the two-story apartment buildings. The ancients did ok.