best places to visit in china

hi all
I am planning to come to a trip of china,japan because of my company's deals. Can you please inform me about some beautiful cities, that I must have to visit. And definitely about the best tracks near my living place. My visit will be of 15-20 days, and the target cities are shanghai, Beijing, Hong kong, and may be taipei. I will be there after 1 month . so I want to plan my trip now.

I like mostly shanghai and hong Kong both are very beautiful city in the china, I go many time in both city I like personally there lifestyle of the peoples.
There is a mostly peoples are working at the night and day , This both cites are never sleep. I love there night life.

I prefer shanghai and beijing wonderful place to visit. Don't forget to visit "Great wall of China".