Maybe this title is misleading. I always thought of the whole complex is called simply: Pyramid of the Sun. It sure is the main draw, in the sense that it is the largest thing in the whole park, but maybe Teotihuacan is more correct term of this place.
What you get there is an old pre-Columbus city filled with pyramids built around a main walkway called the Avenue of the Dead. Dead only by name. It is a nice 1 hour bus ride to the northwest of Mexico City, and takes about half a day for a nice and easy trip. Budget 2-3 hours for the transport (return trip), and another 2-3 hours for for Teotihuacan itself.
Before we start, please remember that the altitude at Teotihuacan is 2300m above sea level (measured on my GPS), so unless you’re from Quito, Ecuador, it is most likely you will tire a lot more easily than back home. So bring water, walk, rest, climb a bit and rest even more.
During the trip, I packed a Tom Bihn Aeronaut 45 Packing Cube backpack which is light and has this nice bottom compartment that fits a 1.5L bottle of water easily. Tom Bihn makes great stuff. Other than that, I had my camera, sketchpad, portable battery and a down jacket in the bag.