Limestone Towers, Madagascar

Photograph by Stephen Alvarez, National Geographic

A city of limestone towers rises in western Madagascar. Sharp, steep, and brittle, the maze of rock in Tsingy de Bemaraha national park and reserve has repelled all but a few explorers and scientists, leaving large parts of the region—and countless resident creatures—unknown to humans.

(For more pictures of the amazing colors of our world, buy the National Geographic book Life in Color.)