The Roman Empire at its height

In 117 AD, under the emperor Trajan, the Roman Empire reached its greatest territorial extent, stretching from the Atlantic coast of Iberia to Mesopotamia, and from the deserts of North Africa to Hadrian's Wall in northern Britain. For the first and only time, the entire Mediterranean was a Roman lake, ringed by a single state that its people simply called mare nostrum, "our sea".

Drag the ChronoAtlas timeline across the centuries and you can watch Rome grow from a central-Italian city-state into this vast empire, then fracture, shrink and finally fall in the west by 476 AD while the east endured as the Byzantine Empire for another thousand years.

Key facts

• At its peak the empire covered around 5 million km2 and ruled perhaps 60-70 million people, a fifth of humanity at the time.
• A network of over 400,000 km of roads, 80,000 km of them paved, tied the provinces to Rome - the origin of "all roads lead to Rome".
• The city of Rome itself passed a million inhabitants, a size no European city would reach again until 19th-century London.
• Trajan's successor Hadrian pulled back from the eastern conquests and fortified the frontiers, marking the shift from expansion to defence.