Nitra

City · c. 814 CE · in Europe

Capital of Principality of Nitra (814–839).

Mashhad (818 CE): Capital of Afsharid Iran (1736–1756).
Aínsa (c. 825 CE): Capital of Kingdom of Sobrarbe (825–829).
Yasodharapura (c. 802–1431 CE): Capital of Khmer Empire (802–1431).
Hariharalaya (c. 802–1431 CE): Capital of Khmer Empire (802–1431).
Prague (800 CE): 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).
Heraklion (c. 830 CE): Capital of Emirate of Crete (830–960).
Jaca (c. 830 CE): Capital of County of Aragon (830–921).
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).

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.
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).
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.
Treaty of Verdun (843 CE): Treaty dividing the Carolingian Empire among three grandsons of Charlemagne, roughly foreshadowing France, Germany and Italy.
Alfred the Great (849 CE – 899 CE): King of Wessex who defended his kingdom against the Vikings, reorganised its defences and promoted learning in English.
Palermo (c. 850 CE): Capital of Emirate of Sicily (850–1091), Kingdom of Sicily (1139–1266), Kingdom of the Two Sicilies (1815–1860).