From National Geographic:
The light beaming from above reveals a tower of calcite on the cave floor that is more than 200 feet tall, smothered by ferns, palms, and other jungle plants. Stalactites hang around the edges of the massive skylight like petrified icicles. Vines dangle hundreds of feet from the surface; swifts are diving and cutting in the brilliant column of sunshine. The tableau could have been created by an artist imagining how the world looked millions of years ago.
Photo gallery with many more images, all shot by Carsten Peter for Nat Geo.
(Via Submitterator, thanks Marilyn Terrell!)