Kartchner Caverns State Park is known for its diversity of minerals. On March 1, park staff spotted one that's particularly ...

Usually less than 30cm wide, they are found in shallow pools of water in limestone caves and form when layers of calcite build up around a nucleus, often a fragment of rock or piece of mud.

They had crawled into Cave of the Winds, deep inside a cave system known as Clearwater ... drilling and hammering bolts into the slick rock to hold their climbing ropes, their odds of success ...

Deep inside a labyrinthine cave in southwestern France, ancient humans who lived around 30,000 years ago carved horses, mammoths and rhinoceros into the walls, a fabulous prehistoric menagerie that ...