An abandoned saucer-shaped monument in the Bulgarian mountains.

This cluster of little wooden huts once ground local farmers’ wheat into flour during the days of the Austro-Hungarian Empire.

A unique opportunity to stay the night in retrofitted sections of sewer pipe.

Austria's very first and only nuclear power station was completed but never used.

Vienna's underworld of tunnels and subterranean rivers made an iconic appearance in a 1949 Orson Welles film.

The former private quarters and office of Dr. Sigmund Freud now hosts a museum housing the works of the founding father of psychoanalysis.

Anyone wanting to know what a dwarven mine sounds like need only visit the tunnels of this New Zealand artillery compound.

Deadly scalding and one of the largest hot springs in the world.

These phallic stone spires once served as Tolkien's Paths of the Dead.

Some of the clearest water anywhere in the world.

One man's dream has turned into this naturally growing chapel made of almost nothing but trees.

This strange geological landscape erupts with sudden bursts of water.

The most southerly spot on New Zealand's South Island is home to surreally shaped, permanently mangled trees.

One of the world's largest Tesla coils.

A solitary tree has grown up all alone on Lake Wānaka, backdropped by the beautiful Southern Alps.

Sail in for a ’dam good slice.

This canyon is comprised of gorgeous waters and magnificent basalt columns.

A Wes Anderson-esque lighthouse that boasts magnificent coastal views.

A world-class theater sits hidden in this remote town in West Iceland.

Climbing Iceland's highest peak on the rim of the Oræfajökull volcano.

Outlaws, hot springs, and tragedy have all left their mark on this ancient road in the Icelandic highlands.

An Icelandic island full of diving birds and legend.

The Arctic Circle runs through this isolated spot north of Iceland.

A giant concrete orb in far north Iceland marks the ever-shifting boundary.