From Terminal Norte, purchase your ticket to T-E-O-T at Gate 8, chances are that's as near as you'll get to pronouncing it before you notice the word PYRAMIDS written on the ticket board. At 23 pesos it seemed almost sacreligious.
It's best to get there early--a 9am bus is just chipper, but don't forget the munchies, as your stomach will unleash a heartfelt roar by the time you arrive.
I recall as we approached the site the immense surroundings that encompassed the area. As the bus drew nearer, it became obvious that in fact my presumed mountain was the Pyramid of the Sun. My heart was in my mouth, and my brain was rattling like a pensioner in a supermarket looking for cheap biscuits.
You can't help but be drawn to its presense. I don't recall the walk to the entrance (except the Voladore pole situated among 10-foot cacti, which looked ropey to me). As you stand on the main concourse and look up at the Pyramid of the Sun, you can understand why the Aztecs may have had this as the center of their universe. It's immense--275 feet at the base, but the secrets within are what intrigued me.
The Maya/Olmecs, who were originally responsible for the thirteen skulls, passed them onto the Aztecs. At Teotihucan, they resided in the center of the Pyramid of the Sun (you can see the entrance door). These skulls, of which there were thirteen, held the contents of knowledge from the twelve other planets that are inhabited. (The thirteenth skull contained all the knowledge.)
During Cortes' march to Teotihucan, he became informed of the skulls by neighboring tribes. Under the Pope's orders he was told to retreive them. The jaguar warriors heard of this plan and before his arrival scattered the stones. It is a mystery to this day as to where they are scattered. But it is proclaimed that one day these stones will unite in a time of crisis.
The walk to the top of the Pyramid of The Sun isn't for the faint hearted. But take heart (no pun intended), when I arrived I wasn't stretched over a sacrifical stone and my heart torn with a clever bit of obsidian (lucky that). But the solitude of being the only person there, helped accentuate the whole feeling connected to the place.
As a place to go, it is essential. You will leave feeling empowered, and mesmerised by the achievements of what historians like to call a primitive society.