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3. Tsaritsyn
Name of the s under Tsarist Russia
4. Byzantium
Byzantium was the original Greek name of the city.
6. Peking
Peking was the Romanised version
9. Lundenwic
After Londinium was abandoned, the Anglo-Saxon settlement on the site was named Lundenwic
10. Pest-Buda
This seems pretty self explanatory
12. Nur-Sultan
The name change was temporary and controversial, being reversed three years later.