Mexico’s Caribbean, an earthly paradise of white sand beaches, blue sky and rolling sea, is both very ancient and still in the process of being born. South of Cancun’s wall-to-wall high-rise hotels is a very different world. That is where the Riviera Maya begins, a peaceful stretch of coastline blessed with bounteous flora and fauna, an idyllic climate and a storied past. Among the places to explore the Riviera Maya’s natural attractions are The Great Maya Reef, a 218-mile treasure-trove of corals, fish and other marine life, accessible from the fishing village of Puerto Morelos; the Sian Ka’an Biosphere Reserve, near Tulum, which includes savanna, coast and tropical forest, and its attendant wildlife; Cozumel, a sacred place for divers and snorkelers since Jacques Cousteau filmed it in 1961 and the site of Laguna Chankanab, a national park with botanical garden and reproductions of Maya buildings; Xcaret, an eco theme park with butterfly pavilion and subterranean river system; Xel-Ha, a lagoon and natural aquarium full of iridescent fish.