Kukulkan, a benevolent alien being, visited the ancient Earth civilizations and influenced their architecture and agricultural development. Kukulkan was worshiped as a god by the Mayans who encountered him. Kukulkan gave the Mayans their remarkably accurate calendar and told them to build a city according to its cycles. On the date the city was finished, Kukulkan was supposed to return. The Mayas built their city but Kukulkan never appeared. As they had only built parts of the city, they had not finished the energy amplification system that was supposed to signal Kukulkan.