A fearsome stone serpent head juts from the balustrade of the Temple of Quetzalcoatl at Teotihuacan, its obsidian-red eyes still vivid against aged volcanic rock — one of the most iconic details in all of pre-Columbian archaeology. Shot from atop the Ciudadela complex, the composition draws the eye down the steep staircase toward the broad Avenue of the Dead, with the massive Pyramid of the Sun rising in the middle distance beneath a cloudscape of cotton-white cumulus. Teotihuacan, which flourished roughly 100–650 CE and may have housed 125,000 people at its peak, remained one of the hemisphere's most visited archaeological sites throughout the mid-20th century, making souvenir chrome postcards like this a staple of Mexico City gift shops.