The Bent Pyramid, Dahshur — built for Pharaoh Sneferu around 2600 BC, the most vivid surviving record of ancient engineers solving a design problem in real time. Construction began at 54 degrees, then abruptly shifted to 43 degrees halfway up. Uniquely, it retains nearly all of its smooth outer limestone casing — the closest thing to seeing what Giza once looked like.
© Lexie, CC BY 2.0, via Wikimedia Commons
