There are also 500. Let's not talk about those less than 500 years old, those with less than 1 10,000 employees or those that don't exist now. Just say a few categories instead of five, and some have reached the level of world heritage.
Water conservancy projects: Beijing-Hangzhou Grand Canal, Dujiangyan;
Military engineering: Ming Great Wall;
Civil engineering: Forbidden City;
Comprehensive system engineering: Hani terrace;