A tiny microvalley etched into the side of Knocknarea Mountain hides another world.

Panorama exhibition hall in old silent theater with a beautiful backyard garden.

Vortex-shaped aquarium hosts Europe's largest school of piranhas and other ocean creatures.

The hidden "ballroom" under a mansion lake was built by a criminal who ate a cyanide pill during his trial.

Countless stories attempt to explain Poland's mysterious J-shaped trees.

Each year melting snow turns these Austrian hiking trails into scuba zones.

For two weeks every June, fireflies in the Smoky Mountains perform an astonishing light show.

Half of a waterfall goes into the river while the other half seems to disappear.

A naturally beautiful, seemingly bottomless deep blue spring.

Stalactites and stalagmites in a beautifully lit cave.

Mural made of 100,000 pieces of hand blown glass, and until recently, the largest glass mural in the US.

Trick water gardens from 1619 featuring a 200 piece mechanical theater powered by water.

New fungal and bacterial species call this deadly lake home.

A mysterious light floating in the trees of Arkansas may be a piezoelectric effect.

Roman ruins top white travertine terraces formed by ancient hot springs.

A spectacular cave and a beguiling lake.

A roaring, awe-inspiring double cascade of icy water flows through woodland Oregon like something out of a Tolkien novel.