Naples

City · c. 763 CE · in Europe

Capital of Duchy of Naples (763–1137), Kingdom of Sicily (1266–1282), Kingdom of Naples (1285–1805), and 2 more.

Nekor (c. 760 CE): Capital of Emirate of Nekor (760–1019).
Aachen (c. 768 CE): Capital of Kingdom of the Franks (768–843), Middle Franks (855–899), Holy Roman Empire (962–1346), and 1 more.
Córdoba (c. 757 CE): Capital of Emirate of Córdoba (757–929), Caliphate of Córdoba (936–1031).
Shangjing Longquanfu (c. 756–785 CE): Capital of Balhae (756–785).
Temsamane (c. 750 CE): Capital of Emirate of Nekor (750–760).
Tiaret (c. 778 CE): Capital of Rustamid dynasty (778–909).
Dali (c. 779 CE): Capital of Nanzhao (779–902), Kingdom of Dali (947–1253).
Malamocco (c. 742 CE): Capital of Republic of Venice (742–810).
Fez (789 CE): Capital of Idrisids (793–974), Marinid Sultanate (1250–1465), Wattasid dynasty (1472–1554), and 1 more.
Koumbi Saleh (c. 793–1200 CE): Capital of Ghana Empire (793–1200).

Around the same time and place

Charlemagne (c. 747 CE – 814 CE): King of the Franks who conquered much of Western Europe, was crowned emperor in 800 and promoted a revival of learning, the Carolingian Renaissance.
Battle of Tours (732 CE): Frankish forces under Charles Martel defeated an Umayyad army between Tours and Poitiers, halting Arab expansion into Gaul.
Coronation of Charlemagne (800 CE): Pope Leo III crowned Charlemagne emperor in St Peter's Basilica on Christmas Day, reviving the imperial title in the West.
Trier (16 BCE – 1618 CE): Capital of Electorate of Trier (1333–1618).
Prague (800 CE): Capital of Duchy of Bohemia (896–1002), Kingdom of Bohemia (1202–1528), Holy Roman Empire (1346–1611), and 4 more.
Carolingian minuscule (c. 780 CE): Clear, standardised script developed in the Carolingian Empire; it is the basis of modern lowercase letters.