El Tajín

de bene esse: literally, of well-being, morally acceptable but subject to future validation or exception

Mesoamerica 

El Tajín flourished from 600 to 1200 AD, and during that time numerous temples, palaces, ballcourts, and pyramids were built. 

Once the city fell in 1230 until nearly the end of the 18th century, no European appears to have known of its existence, until 1785.