Chichén-Itzá is an archeological site located in the Yucatan and is considered to be the best-preserved Mayan city on the peninsula. Many of the doubts that scientists had about the Mayan calendar and Mayan science, in general, have been removed by studying this fantastic place. You can hear all the stories from the guide when you arrive at this UNESCO World Heritage Site. Be prepared for an overcrowded, humid, and hot place, but sure worthwhile visiting.