A forgotten and crumbling Yugoslav monument to the victims of fascism.

A tower marking the spot where Yugoslavia began its resistance against the invading Nazis stands neglected, but not quite forgotten.

This rusting remnant of the local herring industry is being given a second life.

A micro-communist utopia in Spain with no police, no mortgages and full employment.

This abandoned fishing settlement may well be the greenest village in the world.

Sections of the iconic limestone columns have been left uncleaned as a reminder of the city's polluted past.

The subterranean "lake" below the Paris opera house inspired the Phantom of the Opera's lair.

The designer of this railway tunnel added a birthday present for himself.

Abandoned tunnels dug for the once-thriving sea salt industry on the coast of southern Spain.

Once home to Komodo dragons, this island dreamscape has a rare combination of white, pink, and black sand beaches.

Thousands of letters to Santa get delivered to this mailbox in Greenland.

A rare pod of derelict midcentury Futuro and Venturo houses lines a semi-abandoned beachfront resort outside Taipei.

The peaceful space is adorned by paintings by the famed abstract artist Mark Rothko.

This daunting 1st century fortress was purportedly the site of one of the most dramatic revolts of the Jewish-Roman wars.

This 3,800-year-old site contains markers used to study the movement of the sun and moon and create a lunar calendar.

There was a top secret plan during World War II to seal a group of soldiers inside the rock.

A half-mile long and three stories high, this bridge over the Des Moines River Valley mimics a descent into a mine shaft.

Spanning over 10,000 square miles, this ancient salt pan is one of the largest on the planet.

The storied English village that pretended to be insane inspired NYC's nickname and the fictional namesake in the DC Comics universe.

A controversial artwork draws attention to the dark history of Prague's "Suicide Bridge."

A remarkably well preserved tower dating all the way back to the Iron Age.

The geoglyph once sported a glass bottle eye.

A rare opportunity to drive across the ocean floor.

A 14th-century European chapel sticks out of the facade of a Japanese hotel.