Heraklion

City · c. 830 CE · in Europe

Capital of Emirate of Crete (830–960).

Jaca (c. 830 CE): Capital of County of Aragon (830–921).
Aínsa (c. 825 CE): Capital of Kingdom of Sobrarbe (825–829).
Samarra (c. 836–892 CE): Capital of Abbasid Caliphate (836–892).
Mashhad (818 CE): Capital of Afsharid Iran (1736–1756).
Nitra (c. 814 CE): Capital of Principality of Nitra (814–839).
Kashgar (c. 850 CE): Capital of Kara-Khanids (850–1045), Eastern Kara-Khanids (1046–1138), Western Karakhanid Khanate (1046–1084), and 4 more.
Palermo (c. 850 CE): Capital of Emirate of Sicily (850–1091), Kingdom of Sicily (1139–1266), Kingdom of the Two Sicilies (1815–1860).
Balasagun (c. 850–1218 CE): Capital of Kara-Khanids (850–1045), Eastern Kara-Khanids (1046–1138), Western Karakhanid Khanate (1046–1084), and 1 more.
Gangaikonda Cholapuram (c. 850 CE): Capital of Chola Empire (850–1259).
Yasodharapura (c. 802–1431 CE): Capital of Khmer Empire (802–1431).

Around the same time and place

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.
Palmyra (c. 261–1929 CE): Capital of Palmyrene Empire (261–269).
Sibenik (860 CE): Capital of Kingdom of Croatia (926–1098).
Olbia (c. 866 CE): Capital of Giudicato of Gallura (866–1209).
Edessa (302 BCE – 1150 CE): Capital of Kingdom of Osroene (63 BCE–214), County of Edessa (1099–1150).
Chufut-Kale (500–1490 CE): Capital of Crimean Khanate (1450–1490).