Dujiangyan Irrigation Project

Dujiangyan (Du Gon Yen) City is a 2,200 year old water irrigation municipal construction project. It was built in 220 BC and amazingly only took 15 years to build.
The river is very big, long, and quite fast. In the wet season it would flood the crop fields and in the dry season not enough water could reach the crop fields.
Either way, a farmer’s nightmare.
So a self taught Civil Engineer named Li Bing had a bright idea (another one of those “Hey, guys, I have an idea ...” moments) to build an island in the middle of this very fast flowing river to split the river into two sides. One side would be narrow and deep so the river would flow to this side in the dry season and concentrate the water towards the farm land, and the other side would be wide and shallower to accept the river in the wet season to prevent flooding by diverting a majority of the water away from the fields. They built a dam on the wide side and by careful control of the dam opening they could divert the water to where they needed it. Using rocks and Bamboo rope, they built this monstrous place.
Today, the dam has been replaced by a modern dam, but the entire system has withstood 2200 years of man and is still how the Sichuan region acquires all of its water needs. There is a big celebration twice each year when they open/close the dam to change the water flow.
Quite a legacy for a 2,200 year old engineer who used an abacus to figure it all out (who needs Auto-Cad 3D modeling?)
The bridge is a free swinging contraption that requires good balance to cross. It has been replaced through the years but is always built the same way as the original with all natural materials (not too high, but still a bit unnerving to cross when you consider falling into the rapids below if something breaks). I looked for nails, bolts, screws, steel cables, etc and couldn’t find any.
I have long been impressed by the building of our Ft. Sumter in Charleston which was also built by dumping rocks in the harbor until an island formed – but we failed in comparison of magnitude!
And the Chinese built this 2,000 years before we had the same bright idea.