Since the reign of Roman Emperor Augustus ( end of first century BC ) , the northern border of the peninsula has been set on the Alps watershed , but geographically it coincides with a line extending from the Magra to the Rubicon rivers , north of the Tuscan-Emilian Apennines , which excludes the Po Valley and the southern slope of the Alps .
Since the reign of Roman Emperor Augustus ( end of 1st century BC ) , the northern border of the peninsula has been set on the Alps drainage basin .