Sewers and paved roads are what really boggles my mind, most in the last half-century. Or that China used more cement in 3 years than the U.S. did in the entire

Sewers and paved roads are what really boggles my mind, most in the last half-century. Or that China used more cement in 3 years than the U.S. did in the entire 20th century. We're living in an era where things like the Great Wall of China or the Hanging Gardens of Babylon are created on a regular basis. I just hope this progress isn't sigmoid shaped, or that we've more than passed the half-way mark.