The names of five ancient projects?

There are five hundred. Let's not talk about those less than five hundred years old, those with less than 1, workers or those that don't exist now. Just name a few categories instead of five, and some of them have reached the level of world heritage.

Water conservancy projects: Beijing-Hangzhou Grand Canal and Dujiangyan;

Military engineering: Ming Great Wall;

civil engineering: the Forbidden City;

comprehensive system engineering: Hani terrace;