The date for the founding of Rome is rather controversial, and far from all historians agree on it. And nothing really survived from the early period - though yes of course, the people who populated the settlement built it at that time.

The people who lived here built their own dwellings too, fifty years ago. They don't now, do they? And in Rome, stuff like the Aqueduct (built entirely using slave labour), as well as countless other landmarks, survive to this day.