About 50,000 miles (80,000 km) of road spread across Roman civilization. It influenced the western world. They built strong arched bridges (built of course, in a Romanesque style) .Mastered the concept of "running water" using aqueducts that, among other things, supplied public baths similar today's modern water facilities.
At the peak 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). Or as much as 1/5 of the world's population (60 million people) claimed Roman citizenship and as many as 120 million people may have lived within the boundaries of the empire. (As shown in the map in my last blog.)