By HJPD - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=6854409
The Toltecs are a mysterious Mesoamerican civilization. They built the city of Tulla, in modern state of Hidalgo, Mexico. They dominated central Mexico, only to vanish before the arrival of the Mexicas.
Some people think that the Toltecs were actually extraterrestials, and that Tulla was one of their bases. After they carried out their mission, they got in their flying saucers and left the earth. They had come to share their philosphy, culuture, and technology, but humans rejected them, so they left us.