Sian Ka’an means “where the sky was born” in Mayan. It’s an apt name for the 2,500-square-mile peninsula about 75 miles south of Cancún, where ocelots, monkeys, pumas, and more than 300 bird species patrol the jungles and skies. It’s also home to clear-water lagoons and coves teeming with manatees, rays, crocodiles, and sea turtles swimming toward their nesting grounds. The biosphere reserve is a World Heritage Site, with fewer than 1,000 residents and just a few campgrounds and fishing lodges. Set up a tour of the canals dotted with small Mayan ruins through the Sian Ka’an Visitor Center.