The Great Pyramid of Khufu, Giza — the only one of the Seven Wonders of the Ancient World still standing, completed around 2560 BC using an estimated 2.3 million stone blocks averaging two and a half tons each. At 481 feet tall, it held the record as the tallest structure on earth for 3,800 years. No one has ever found a contemporary written account of how it was built.
Warren LeMay from Chicago, IL, United States, CC0, via Wikimedia Commons
