Teotihuacan is a small city near Mexico city, it’s conveniently located so one day trip is certainly a possibility.
The Pyramid of the Sun is the largest building in Teotihuacan (height is 71 meters), believed to have been constructed about 200 CE, and one of the largest in Mesoamerica. Found along the Avenue of the Dead, half way to the Pyramid of the Moon.
I’ve heard that steps on pyramids are made huge on purpose, back in the days people were a bit shorter so huge steps forced them to climb on knees when they were reaching the top, so that when they face gods they would be already on their knees.
As a reward for all the efforts you can enjoy picturesque views from the top of the pyramid.
At the end of Road Of The Dead you can find some small pyramids and the big one called Piramide De La Luna.
On my way back to main entrance I decided to stay off the main path and explore surroundings a bit. Nothing special, just burned desert and cactuses. From above this looked more promising.