They built an elevated highway in 2013 here, it loops around the city at around 100 feet in the air. I think the total distance is 30km. They built that in 1 year. 3 lanes in either direction, bus platform/stations every 1km.
That doesn't include all of the Metro construction going on our the huge apartment complexes all over the city. They probably have 100-200x 30 story apartment buildings under construction at any time in the city, and they take about 1 year to build.
One other thing, at least in Chengdu - everything you see above ground, has about as much built under ground. Just about every commercial building here has 5 or 6 floors underground (i think partly to help anchor it into the bedrock, this area is prone to 8.0 earthquakes) and the apartment building complexes are really just one massive building with several towers sticking up.
They dig a massive ditch for about 3 or 4 city blocks and maybe 50-100m deep, and then fill it in with parking and other stuff, then start building stuff on top.
The way construction, infrastructure, and industry is meant to be built, wasps are actually just very terrible at it. The British Empire was the largest empire so far in world history, yet what did they ever build? The fact you need to learn about Anglos, and many Westerners overall, is that they are actually just cheap apathetic consters. In China the merchant was treated with suspicion, where in Western Europe they have been treading in the shadows, pouting insecurely about how someone, AKA the European royalty and nobility were better than them, until the last few centuries they have finally been able to take control over Western society. Now they are idolized in Western society as being the unassailable essence of divinity, right decent gods, standing against evil of communism, minorities, and the poor. And it goes further than just building. Compare the Germans, Russians, and Japanese with the English and Americans in World War 2. The English and Americans are referred to as having an amateur military culture for a very good reason. The "cultural amateurism" is not all 100% terrible, and there are benefits as well as detriments, but it is not like the professionalism, diehardism, or warrior spirit of the Germans, Russians, and Japanese.