Barcelona had been settled centuries before by
Phoenicians, and the Carthaginian Empire had made Barcelona a commercial
port. In the first century B.C.E., the Romans took over. Then, with the
disintegration of the Roman Empire came the Visigoths, who named to city
Barcinona. In the 700s, Islam's Moors conquered Barcelona. Continuous fighting took
place in the area between Christian and Islamic forces. Charlemagne took the
city, and, after him, his son Louis the Pious established a strong military
presence in Barcelona.
In Rome, on Christmas Day in CE 800, as Charlemagne knelt at St. Peter's, Pope Leo III placed a gold crown on his head and declared him emperor. This implied Roman emperor, and the Byzantines were outraged. They believed that the Roman Emperor resided in Constantinople and that Charlemagne was a barbarian. Pope Leo III saw the Christian church centered in Constantinople as a rival.
Aachen was Charlemagne's favorite place to reside. His northern capital, where he built a palace and founded the cathedral that today contains his tomb.
Paris had been the capital of the barbarian Frankish king Clovis (466-511). Under the Charlemagne it was largely ignored and in decline. Charlemagne visited it no more than four times.
Venice was under the rule of Giovanni Galbaio and allied with Constantinople.