<P> During the 5th century BC, Rome gained regional dominance in Latium, and eventually the entire Italian peninsula by the 3rd century BC . The population of the city at this point is estimated at about 310,000 people . </P> <P> With the Punic Wars from 264 to 146 BC, Rome gained dominance over the Western Mediterranean, displacing Carthage as the dominant regional power . The Roman Empire was established under Octavian in 27 BC, after Julius Caesar's conquest of Gaul, followed by a period of civil war . The city of Rome now surpassed a population of one million, likely the first city in history to reach this size (compared to world population of about 200--300 million at the time). </P> <P> At the peak of Roman imperial power in the 2nd century, the population of the city numbered about a million people, a size that it never attained again until its becoming the capital of the Republic of Italy in 1946; close to three percent of the population of the empire lived within its limits . Following the Crisis of the Third Century and the transfer of the imperial capital to Constantinople in AD 330, Rome entered a period of gradual decline . </P> <P> After the collapse of the Western Roman Empire, Rome managed to hang onto the empire, still known as the Roman Empire but long centered on the eastern Mediterranean, until the 8th century as the Duchy of Rome . But the city was reduced to a fraction of its former size, being sacked several times in the 5th to 6th centuries, in 546 even temporarily depopulated entirely . With the final loss of imperial control in Italy, Rome became the capital of the Papal States in medieval Italy . The Papacy struggled to retain influence in the emerging Holy Roman Empire, and during the Saeculum obscurum, the population of Rome fell to as low as 30,000 inhabitants . Following the East--West Schism and the limited success in the Investiture Controversy, the Papacy did gain considerable influence in high medieval Europe, but with the Avignon Papacy and the Western Schism, the city of Rome was reduced to irrelevance, its population falling below 20,000 . </P>

What was the population of ancient rome at its height