World’s Strangest Natural Wonders
<a href="http://www.flickriver.com/photos/38235519@N05/popular-interesting/" target="_blank" rel="nofollow">Robert O'Duill</a>
Marble Caves, Chile
Six thousand years of wave erosion created the undulating patterns that give these caves their marbleized effect, enhanced by the reflection of the blue and green water of Carrera Lake, near Chile’s border with Argentina. Although the area is threatened by a plan to build a dam nearby, for now, visitors can kayak throughout the caves on days when the waters are calm.