Where would be the best place to build a new city in ancient china?

Near the Chang Jiang (Yangtze River) along the Eastern coast would be the best place to settle. It would provide fresh water for farming, flat land, and access to the sea for trade and travel. You would not settle near the Huang He (Yellow River) because it floods. One advantage for the Eastern coast is that it provides access to the East China Sea. The Central advantage is that since it's so far into China, it would take enemies longer to reach them. An advantage in the Western section is that there are mountains for protection.

This is the city that would have the greatest success if that is what you need. I hope that helps :). Have a great day!