I'd hesitate on calling it the cleanest nicest city in China though, it's capital of a big rustbelt -long one of China's richest regions back when coal, steel and heavy industry was a thang, now in decline as the national demand becomes more eco-friendly. All of China's big cities are lean, green and super clean now in part thanks to Big Brother and the powerful environment lobby.
For example this is a third/ second tier city famous for its night markets, far inland and insanely crowded. Yet try and spot any crumb of rubbish:
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