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The capital cities of Kaifeng and subsequently Hangzhou were both the most populous cities in the world for their time , and encouraged vibrant civil societies unmatched by previous Chinese dynasties .
 Kaifeng, Hangzhou
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 Kaifeng, Hangzhou