Calakmul Biosphere Reserve

UNESCO-listed as both a natural and cultural World Heritage Site, Calakmul in Campeche contains the Maya ruins of a city that once rivaled Tikal in political power within an 1.8-million-hectare tropical forest that hosts jaguars, tapirs, spider monkeys, and the largest population of scarlet macaws in Mexico. The site's dual heritage status is unique in the Americas.