Teotihuacan

Prehispanic city known as "The God's City" , occupied approximately
from 200 B.C. to 750 A.D. site of great importance for all mesoamerica
due to the leyend of the fifth sun, which was created here. 

(Pardon the translation - I copied directly from the postcard)

Thank you Danielle! She brought this postcard back from her trip to Mexico this summer.