Abandoned railway line circling the city of Paris.

The largest catacomb system in the world.

The vast, legendary catacombs hold secrets much stranger than stacked bones.

An ultra-modern diversity park in Denmark has turned an entire city block electric pink.

This space rock fragment is one of the only meteors to have ever struck a human.

The Uyghur settlement in the middle of a lake continues to raise questions.

The old Niles Canyon Aqueduct in the San Francisco Bay Area is a bemusing and secret trail through nature for wayward travelers.

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

America's oldest archaeological site or a muddled case of wishful thinking.

Discovered by cows, these upstate New York show caves are presented with a healthy dose of psychedelic folk art.

The longest navigable underground river in the United States is home to countless blind and albino animals.

The second largest in the world, this massive underground void has its own subway.

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

Abandoned Japanese ghost town gives a glimpse into what our own metropolises may leave behind.

Local legend says that whoever burns down this 2,000-year-old tree will only have seven days to live.

A derelict New Zealand-themed amusement park in Japan.

450 dead and frozen fish, proudly on display in Japan.

The longest living non-clonal organisms on Earth.

A sculpture that resurrected the only tree standing following the devastating 2011 tsunami.

One of the world's oldest and most massive living organisms is a grove of quaking aspens.

A tree grown from astronaut seeds which were exposed to cosmic rays.

Home to Hollywood history and a very special salt crystal.

Island ghost town detailing Flagler's folly in building the Overseas Railroad.

An exquisite tunnel of cascading flowers.