They had historians, and those historians had access to material that long ago went into the first on a cold night. The amount of construction done by the Roman Empire gets a little more stunning every year, in the case of Germany etc the discovery of a long term Roman presence in areas not previously allowed by the little too sure of themselves set.
Quibble -- the empire started with the conquest of Ostia, and ended at last with the Turks' conquest of Constantinople, 18 centuries.
“18 Centuries...”
Damn, almost TWO thousand years...
“The amount of construction done by the Roman Empire gets a little more stunning every year”
They had some SERIOUS engineering skills, for sure.