This is the 3779th most frequent Chinese word.
郑州
Zhengzhou: A major city in central China and the capital of Henan Province.
In this sentence, '郑州' functions as the proper noun referring to the city and the destination of visitation.
我去年去过郑州游玩。
I visited Zhengzhou last year.
Here, '郑州' is again a proper noun being used as the subject of the description regarding its historical significance.
郑州是一个历史悠久的城市。
Zhengzhou is a city with a long history.
In this example, '郑州' represents the geographical and administrative entity functioning as the capital of Henan province.