Roman Empire The Roman Empire was one of the largest and most enduring in world history. The saying "All Roads Lead to Rome" alludes to this central hub of technology, literature, culture and architecture in the ancient world. The engineers of the Roman age created an unparalleled network of roads in ancient history. Approximately 50,000 miles (80,000 km) of roads spread Roman civilization, influence and the mighty legions throughout the western world. They built strong arched bridges, and mastered the concept of "running water" using aqueducts that, among other things, supplied public baths rivalling today's modern water facilities. At the height of its power in the 1st and 2nd centuries AD, the Roman Empire consisted of some 2.2 million square miles (5.7 million sq. km). 60 million people (or as much as 1/5 of the world's population) claimed citizenship of Rome and as many as 120 million people may have lived within its borders.