A vast tropical plateau that ranges from rich tidewater estuaries to luxuriant rain forests, the Yucatán Peninsula vaunts no peaks other than those of the great jungle cities of Uxmal, Chichén itza, and Coba. And devoid of mountains, it claims no terrestrial rivers of real note. Yet this area -- from Yucatán's Río Celestum Biosphere Reserve and Dzilbilchaltum National Park to Palenque National Park and Montes Azules

Biosphere Reserve in Chiapas, Mexico -- boasts one of the most spectacular archaeological zones and richest bioregions in North America. This makes up an area dedicated to the preservation of Mayan antiquities, rain forests, coastal waters, and threatened and endangered species that include sharpy eagles, quetzals, toucans, tapirs, flamingos, and Olive Ridley turtles. Here, where American lawyer John Lloyd Stephens once laid waste to "monster alligators," is the continent's best and last stronghold for the jaguar (Panthera onca), revered in ritual prayer and bas reliefs that still adorn the Maya's greatest ruins. Here, too, is the last bastion of the threatened Maya: "Their descendants," Stephens observed more than 160 years ago, "are still in the land, scattered, perhaps, and retired, like our own Indians, into wildernesses which have never yet been penetrated by a white man."