Same Script, Same Cart-Axles
After unifying the six states, the most far-reaching thing Qin Shi Huang did was not the Great Wall, but "same script, same axle-width, same conduct" — unifying the varied writing, measures, cart-widths, and laws of the different states. It was this "standardization" that let a vast and varied territory be effectively governed by one central government for the first time. Over the next two thousand years, dynasties changed countless times, but the political frame of "grand unity" never dispersed — its source lies here.