Three hundred illuminated pillars form an “artificial forest” in Medellín.

One of the earliest—and most commonly forgotten—acts of rebellion against English rule.

A small etching on the white marble parapet was written in runic script by a Viking mercenary.

A meow-velous tribute to a beloved street cat, made famous on the internet.

A marvel of Byzantine engineering under the streets of Istanbul.

A gorgeous, Gaudí-esque stairway constructed in the city of Istanbul by a prominent Jewish family.

This half-forgotten fortress was constructed by the Ottoman conqueror of Constantinople.

This column celebrates Rome's victory over the Goths, and may be the oldest Roman monument in Istanbul.

Propped high atop the peak of Mount Gamsutlmeer, this abandoned village is one of the oldest settlements in the region.

Steam engines and conveyor belts are remnants of a genius system left in the middle of the Maine woods.

These Great Lakes sea caves accessible by boat in the summer turn into temples of ice reachable by foot in the winter.

The largest Walleye statue in the world calls this Minnesota town home.

America's silhouette includes 100 square miles of wilderness jutting into Canada thanks to an old mapmaking error.

Every winter, dozens of otherworldly ice structures sprout up from a rigged up artesian well.

These molds for fiberglass statues have formed an eerie, accidental sculpture park.

"Looks so real, it's scary!"

An old abandoned mining town in The Adirondacks where Theodore Roosevelt first learned of the shooting of President William McKinley.

Teddy Roosevelt’s famous “midnight ride to the presidency" started at this small lake high up in the Adirondacks.

The curious underground history of keeping Paris clean.

A horde of stray cats rule in this secluded Parisian cemetery under a bridge.

Trek up this glacier before it disappears.

Large Hadron Collider and the Birthplace of World Wide Web.

A symbol of friendship between the mountainous regions of Switzerland and Bhutan.

The largest underground lake in Europe.