The early Christian kingdom of Aksum was at the heart of a great maritime trading network. Hundreds of ancient obelisks and stelas are strewn across fields on the outskirts of Aksum, a city in the highlands of northern Ethiopia’s Tigray region. The largest of these monuments, which lies toppled and broken into sections, was carved with doors and windows to mimic a 13-story building, and once stood around 100 feet high. Weighing more than 570 tons, the Great Stela, as it is known, was hewn from a single block of granite-like rock cut from a quarry two and half miles away. At more than three times the height of the biggest of Easter Island’s moai statues and nearly 20 times heavier than the mightiest of Stonehenge’s sarsens, it is among the largest monolithic sculptures ever created and transported.