Teotihucán

Where the Men Became Gods, or so the Aztecs thought. This UNESCO Heritage site is about a hour outside Mexico City. There are daily tours to this site (please bring comfortable walking shoes as there is loads of walking and climbing), or you could take a bus from Autobuses del Norte costing about MXN 28 one-way.

The Pyramids of the Sun and Moon are spectacular and will take your breath away. Else, the climb up one or both of them will! Note that the Temple of the Feathered Serpent is currently closed for restoration.