The Aztec Native American Human civilization existed in the southern regions of North America (an area that later included the nation-state of Mexico) on Earth from the 14th to the 16th century.
Kukulkan, a benevolent alien being, visited ancient Earth civilizations and influenced their architecture and agricultural development. Kukulkan was worshiped as a god and knowledge of his visit was passed on to the Aztecs, who still remembered him in their culture. Kukulkan was discovered by the crew of the USS Enterprise in 2270. (TAS: "How Sharper Than a Serpent's Tooth")
Kukulkan's visit was not given a specific date, but the accounts would seem to suggest an era around 5,000 BC to 2,000 BC.
The hull plating on Federation starships is laid out in what is known as an "Aztec pattern"
In The Art of Alien Worlds", a VOY Season 4 DVD, special feature, matte painting artist Syd Dutton described Ventax II as the "Aztec city of the future".