Watch | Archaeologists explore the once largest city of Americas

Mexican archaeologists are exploring the bowels of the “Plaza de la Luna” (Moon Square) in Teotihuacan for clues into the mysterious ancient city that was once the largest in the Americas.Earlier this year, archaeologists from Mexico's Institute of Anthropology and History (INAH) stepped up investigations at an ancient public square at the ruins after aerial investigations reportedly showed it to be full of craters and passages designed to simulate the universe.Initial excavations at the site have revealed plain stele green stones used by Teotihuacan's ancient inhabitants. Ortega Cabrera said the excavations have added to the importance of the square. Despite being one of Mexico's most-visited tourist destinations, Teotihuacan is so shrouded in mystery that its inhabitants still have no name.