If you compare a map demarcating the outline of the 66- million-year-old impact crater to a map of Mayan ruins in the Yucatán, an unusual pattern jumps out. Sites like the last Mayan capital, Mayapán, are built exactly on the rim of this ghostly ring. And even stranger than the overlap of these two epochal sites—marking the final moments of Mayan civilization and the final moments of the age of dinosaurs— is that it’s not a coincidence. Like any civilization, the Mayans depended on reliable access to freshwater. In the Yucatán, freshwater is provided by picturesque sinkholes in the limestone known as cenotes,which appear as surprising, precipitous oases in the jungle. They form when whole sections of the limestone collapse,providing access to the underground rivers of freshwater that percolate through the chalky sea-rock of the Yucatán. The cenotes made Mayan civilization possible. When plotted on a map, the strange distribution of cenotes in the Yucatán reflects a much more profound disturbance in the rocks far below that is responsible for the limestone collapses in the region. Researchers surveying the archaeological sites that inevitably sprang up among these freshwater sinkholes made a remarkable discovery: Mayan society in the Yucatán traced an improbable 100-mile arc. UNESCO calls it the Ring of Cenotes. Walter Alvarez called it the Crater of Doom.

— Ends of the World by Peter Brannen (49%)