A collection of 1,000 prehistoric structures dubbed mustatils — the plural form of the Arabic term for rectangles — scattered across 124,274 miles (200,000 kilometers) in northwest Saudi Arabia may be the world's oldest monuments. A team of archeologists from the University of Western Australia (UWA) reached this conclusion after radiocarbon dating of charcoal found inside the courtyards indicated they were constructed in 5,000 BC — or about 2,000 years before the Egyptian pyramids or monuments like Stonehenge in southern England.