At its peak in the 1st century BCE, the Roman Republic controlled approximately 2.5–3 million km², stretching from Hispania in the west to Greece and Asia Minor in the east, from southern Gaul in the north to North Africa in the south.

Under Trajan around 117 CE, the empire reached ~5–6 million km² — from Britannia and the Atlantic in the west to Mesopotamia in the east, from the Rhine–Danube frontier in the north to Egypt and the Sahara in the south.