MEXICO CITY, MEXICO—“Large quantities” of liquid mercury have been discovered in a chamber at the end of a tunnel located beneath the Pyramid of the Feathered Serpent in Teotihuacan. “It’s something that completely surprised us,” archaeologist Sergio Gómez of Mexico’s National Institute of Anthropology and History told Reuters. Last year he annouced that three chambers had been found at the end of the tunnel, which had been sealed for 1,800 years. Jade statues, jaguar remains, a box filled with carved shells and rubber balls, metallic spheres dubbed “disco balls,” and pyrite mirrors have also been uncovered. The mercury could indicate that Gómez and his team are closing in on the first royal tomb to be found in Teotihuacan. He thinks that the mercury could have symbolized an underworld river or lake. If there is a tomb, it could help scholars determine how the city was ruled. To read more about Teotihuacan and other ancient cities in the Valley of Mexico, see "Big Data, Big Cities."