The Dolomites

Photograph by O. Alamany & E. Vicens/CORBIS

The rock that makes up the Sella Massif in northern Italy's Dolomites mountain range was once the floor of a shallow, tropical sea. This Triassic-era sea was home to massive coral reefs that built up over millions of years. More recently, glacial erosion carved the Dolomites into their dramatic crags and exposed the reefs and fossils that lay beneath.