The world's largest outdoor organ is played weekly by one of just two civic organists in the U.S.

This massive subterranean fissure is known as the "underground Grand Canyon."

Now abandoned, the world's first torpedo factory is crumbling into the sea.

Oriental bazaar in the heart of Sarajevo.

This museum preserves the hand-dug tunnel that kept Sarajevo afloat during the Serbian siege.

This top-secret nuclear bunker hidden in a Bosnian mountain has been converted to a modern art exhibition space.

A chain of 16 wondrous lakes formed as a result of the gradual dissolution of soluble layers of bedrock.

Yugoslavia's biggest underground airport lies in ruins.

Humble beginnings for one of the world's most famous scientists.

Formerly Yugoslavia's "forbidden island," this sleepy little city still holds the abandoned remains of military strongholds.

An immersive environment that is part haunted house, part choose-your-own-adventure, and part jungle gym.

Get up close to emus and ostriches, or buy their tasty meat.

Rippling sand dunes frozen in the Arizona rock.

The hike through a narrow river flanked by the 2,000-foot-tall walls of Zion Canyon is one of the best in the world.

Just a few miles off the western coast of Ireland lies an isle steeped in Irish literary history.

One of the most popular megalithic sites in Ireland stands as a humbler version of Stonehenge.

The Stonehenge of Wales is one of the grandest neolithic dolmens still in existence.

This neolithic stone grave has been altered and restored so often its now more neo than lithic.

The remains of this deep, dark mine have left behind a haunting rocky warren of tunnels.

This controversial Irish show cave is home to a massive formation known as the Great Stalactite.

A peace symbol in Northern Ireland is among the world's largest hedge mazes.

This singular Irish dolmen is more Frank Lloyd Wright than upright stonehenge.

Once the longest bridge in Ireland, this rusting span sits abandoned and overrun by nature.

Huge standing stones mark a site of megalithic mystery.