Something I'll always remember is this picture of these blacks in Africa scaling down one side of this broken bridge and being pulled up this rope on the other side. The bridge was made out of cobblestone and built over a small canyon. It had been like the bridge had been made by an advanced civilization and the idea to maintain much less repair didn't exist at all. You'd think that someone would go "Hey if we can't do this cobble stone thing, we can repair it with wood, build up from the sides and over, and fix it. But I doubt a single African had that idea go through their head ever.