They had 300 years since the fall of the Western Roman Empire when there was an attempt to rebuild starting from the Frankish kingdom led by Charlemagne (771-814). Pope Leo III crowned Charlemagne Emperor of the Romans on Christmas Eve 800. This caused tensions with the Byzantine Empire which heir of the Roman Empire was also seen
With this crowning the papacy sought to increase their prestige and influence, while Charlemagne reinforced its legitimacy on the territory of the Empire.
The Carolingian Empire or also known as Frankish Empire stretched from the Spanish March to the Elbe and Danube. The capital was established in Aachen where Roman culture was fostered resulting in the Carolingian Renaissance, and Empire was divided administratively into counties and Trademark Ducati, ruled by Counts, Marquis and Dukes.
But the Empire was short. In the year 843 Charlemagne's grandsons: Lothair, Louis and Charles divided the territory triggering a series of territorial reorganization that led to the emergence of new states such as the Franco kingdom that led to France or the Holy Roman Empire that resulted in Germany. The idea of rebuilding the Western Roman Empire and appeared forgot a Europe of different nations with different languages and cultures.