When I was in Mexico City I definitely wanted to visit the site of Teotihuacan. This ancient city is located in a sub-valley of the Valley of Mexico, 40 kilometres northeast of Mexico City. Teotihuacan today is known as the site of many of the most architecturally significant Mesoamerican pyramids built in the pre-Columbian Americas. This site compares in significance to the ruins in Yucatan (e.g Chichén Itzá).
The city's broad central avenue, called "Avenue of the Dead", is flanked by impressive ceremonial architecture, including the immense Pyramid of the Sun (third largest pyramid in the World) and the Pyramid of the Moon.
Climbing the top of the Pyramid of the Sun (almost 250 steps) was rewarded by the amazing overview of the ancient city.