The one-time stronghold of the noble Douglas family, now home to ghost sightings and nesting birds.

Wee (and not so wee) footprints that insects and reptiles of the Paleozoic Era left behind.

Not one, not two, but three natural bridges remain in this captivating spot post-sinkhole.

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

Obelisks and stone pineapples in the Irish countryside.

Ruined 11th century abbey built by King David I in Edinburgh, Scotland.

When the Austin Dam failed it destroyed much of Austin...and then it failed again.

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

Unique geological formations in China, featuring some suggestive shapes.

Twelve sculptures designed to make their best showing with the coming or going of the sun.

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

This unusually shaped mountaintop tower looks like a UFO floating over the city.

A collection of grotesques lines the walls of this Italian villa.

A island reachable by a causeway at low tide is possibly one of the earliest Western European locations to be identified in text.

Ruins of a 10th century church tucked away deep in a botanical garden.

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

A series of gun powder chambers currently hidden from view within Nobbys Headland in Newcastle, Australia.

This immaculate and historic water garden culminates in a massive stone dining table with an inset fountain for chilling the wine of the Cardinal's guests.

One of the most beautiful bookstores in the world hides a neo-Gothic interior behind an art nouveau facade.

A deadly ancient portal to the underworld.

Medieval town turned hippie commune, once home to the secret foreskin of Jesus Christ.

This beautiful natural train tunnel is said to grant the wishes of visiting lovebirds.

Underground hospital complex constructed by slave laborers during the German occupation of the Channel Islands.

The stately remains of Llywelyn the Great's mighty fortress.