After the initial struggles, relationships between the Lombard people and the Latin-speaking people improved. In the end, the Lombard language and culture assimilated with the Latin culture, leaving evidence in many names, the legal code and laws, and other things. The end of Lombard rule came in 774, when the Frankish king Charlemagne conquered Pavia, deposed Desiderius, the last Lombard king, and annexed the Lombard Kingdom to his empire changing the name in Kingdom of Italy. The former Lombard dukes were mostly replaced by Frankish counts, prince-bishops or marquises. In the 10th century Northern Italy was formally under the rule of the Holy Roman Empire but was in fact divided in a multiplicity of small, autonomous city-states, the medieval communes and maritime republic. The 11th century marked a significant boom in Northern Italy's economy, due to improved trading and agricultural innovations, culture flourished as well with many universities founded, among them the University of Bologna, the oldest university in Europe. The increasing richness of the city-states made them able to defy the traditional feudal supreme power, represented by the German emperors and their local vassals. This process led to the creation of different Lombard Leagues formed by allied cities of Lombardy that defeated the Hohenstaufen Emperor Frederick I, at Legnano, and his grandson Frederick II, at Parma, and becoming virtually independent from the German emperors. The Leagues failed to develop from an alliance to a lasting confederation and subsequently, among the various local city-states, a process of consolidation took place; most of them became lordships ruled by powerful families like the Della Scala of Verona or the Visconti of Milan, and conquered neighboring cities threatening to unify Northern Italy under a single state. In the end a balance of power was reached in 1454 with the Peace of Lodi and Northern Italy ended up divided between a small number of regional states, the most powerful were the Duchies of Savoy, Milan, Mantua, Ferrara and the Republics of Genoa and Venice, which had begun to extend its influence in the mainland from the 14th century onwards. In the 15th century Northern Italy became one of the centres of the Renaissance whose culture and works of art were highly regarded. The enterprising class of the communes extended its trade and banking activities well into northern Europe and "Lombards", the term that designated the merchants or bankers coming from northern Italy, were present in all of Europe.