The Ruins of Teotihuacan, Mexico (10/20)

Teotihuacan is an ancient Mesoamerican city that flourished around 200 AD. The city, once home to hundreds of thousands of people, was mysteriously abandoned around 650 AD. Though much of the city’s original structures, including the Pyramid of the Sun and the Pyramid of the Moon, still stand, its empty streets and temples offer little insight into why it was abandoned.