Depending on traffic out of Mexico City, you can get to this mysterious Pre-Columbian pyramid complex in about an hour and a half. It's hot, it's visited by droves of tourists, and there is little to no respite from the sun, but it's worth the schlep to see some of the best preserved ruins in the country. It's still unclear exactly which Mesoamerican group settled down here, but Teotihuacan's influence was felt all the way to Guatemala, and the Aztecs considered it a holy city. With tall, climbable pyramids—some of the tallest in the world—built to honor both the Sun and the Moon, and some incredibly well preserved ancient wall murals, it's a pretty great introduction to Mexico's ancient roots. The temple of Quetzalcoatl is one of the most magnificent looking, decorated with sculptural representations of the plumed serpent god, while the often-missed Tepantitla complex, behind the Pyramid of the Sun, has spectacular frescoes of prominent gods and holy figures in Mesoamerican mythology. Many archaeological findings from the site are at the Museo de Antropología, though the on-site museum provides a solid introduction to the area.