One of the largest barracks of the Austro-Hungarian monarchy's military is now an abandoned ruin.

A hollowed-out baobab that became the horrific final resting place of leprosy sufferers, with gruesome evidence to prove it.

A Lycian city of the dead carved into the hillside of Southern Turkey, complete with startlingly human touches.

Submerged trees jut ghost-like out of an idyllic turquoise mountain lake.

Unusual, mushroom-like rock formations caused by weathering and water erosion, set to disappear, according to geologists.

Eurasia's most difficult place to hang out, and farthest point from sea access.

Keshwa chaca, among the last handwoven Incan bridges, crosses Apurimac Canyon in Peru.

Preserved Inca city and site of the last Inca stronghold against the Spanish conquistadors.

The intricate stonework of Machu Picchu serves as a testament to Incan engineers.

Death rituals and sacrifice inside a Peruvian megalith.

The legacy of a Moroccan Jewish community is remembered at this little mouldering cemetery.

Once the path of a railway tunnel, now home to thousands of glowing insects.

Malaysian fireflies create a dazzling display as thousands light up in unison.

Holy Hindu shrine in an enormous, monkey-filled limestone cavern.

A cave covered with bizarre stalactites of cloth.

Sparkling, calcite-covered skeletons of children who may have been sacrificed to appease an angry god.

A massive underwater sinkhole made famous by Jacques Cousteau.

Extraordinary sculpture garden created by an eccentric English poet.

Risk arrest while partying to fund art.

Visit the site of a subway powered by nothing more than air--and lots of it.

A dilapidated dock tells the story of Titanic's missed arrival.

The oldest surviving bridge in New York City, which reopened to pedestrians in 2015.

A tunnel once abandoned now thrives with graffiti art as an off-limits makeshift gallery.

Whisper secrets in a busy station only to be heard on the other side of this acoustic arch.