medicine,
irrigation,
health,
cheese
education,
baths
and the Circus Maximus
—Monty Python
They got to be an empire thanks to having to respond to invasions and worse by earlier city-states in Italy, and later by the Gauls and the Carthaginians. The first ‘conquest’ by Rome was annexation of Ostia around 500 BC, and the final end to the Roman Empire was the fall of Constantinople in 1453, 39 years before Columbus set forth, iow a run of nearly 2000 years, of course with a lot of ups and downs.