10/29/2010 05:15 pm ET Updated May 25, 2011

27 Amazing Natural Caves (PHOTOS)

When you're planning things to do on a holiday, exploring a cave probably isn't the first activity that comes to mind.

But, as you'll see from the photos we've compiled for you, caves are one of the earth's most fascinating and well-hidden attractions. Crystal, limestone, volcanic rock, ice - these beautiful caves are a geology buff's dream, and a great place to visit for any traveler!

27 Amazing Natural Caves