The first thing I thought when I saw this part of the trailer was the Great Wall of China. My initial theory was that those ships or built the wall (their technology could simulate stone? That's kinda ridiculous) ou built something that the chineses covered up with the wall (similar to the pyramid and the sun-harvester). Yeah, this would be a middle finger from Bay to the human history, but wouldn't actually surprise me after all. Now seen that there are dinosaurs in this scene just ruined my theory. Not that it's a bad thing. Maybe Bay just don't care and decided that the Great Wall was built during the dinosaur age by Cybertronians or maybe it isn't even the Great Wall. Maybe it's actually cyberforming, as RedGoblin once said.