Prague

City · 800 CE · in Europe

Capital of Duchy of Bohemia (896–1002), Kingdom of Bohemia (1202–1528), Holy Roman Empire (1346–1611), and 4 more.

Ribe (800 CE): Capital of North Sea Empire (1018–1035).
Yasodharapura (c. 802–1431 CE): Capital of Khmer Empire (802–1431).
Hariharalaya (c. 802–1431 CE): Capital of Khmer Empire (802–1431).
Kyoto (Heian-kyo) (794 CE): Emperor Kanmu moved the capital to Heian-kyo, which remained Japan's imperial capital until 1868.
Koumbi Saleh (c. 793–1200 CE): Capital of Ghana Empire (793–1200).
Fez (789 CE): Capital of Idrisids (793–974), Marinid Sultanate (1250–1465), Wattasid dynasty (1472–1554), and 1 more.
Nitra (c. 814 CE): Capital of Principality of Nitra (814–839).
Mashhad (818 CE): Capital of Afsharid Iran (1736–1756).
Dali (c. 779 CE): Capital of Nanzhao (779–902), Kingdom of Dali (947–1253).
Tiaret (c. 778 CE): Capital of Rustamid dynasty (778–909).

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.
Viking raid on Lindisfarne (793 CE): Viking raid on the monastery of Lindisfarne in Northumbria, conventionally taken as the beginning of the Viking Age.
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).
Naples (c. 763 CE): Capital of Duchy of Naples (763–1137), Kingdom of Sicily (1266–1282), Kingdom of Naples (1285–1805), and 2 more.
Aachen (c. 768 CE): Capital of Kingdom of the Franks (768–843), Middle Franks (855–899), Holy Roman Empire (962–1346), and 1 more.
Varangians to the Greeks (c. 800–1100 CE): Scandinavian traders and warriors travelled from the Baltic up the Neva and Volkhov past Novgorod, portaged to the Dnieper and sailed down past Kiev to the Black Sea and Constantinople.
Jaca (c. 830 CE): Capital of County of Aragon (830–921).