The old observatory in Copenhagen has a spiral corridor used as a racetrack.

An enormous playhouse designed to look like 21 stacked Lego bricks, with another 25 million colorful Legos inside.

Exquisite wall sculptures carved in secret by an early quarryman in an obscure corner of the Paris Catacombs.

This natural Icelandic fissure allows divers to swim right between two volatile tectonic plates.

Bridge that died in war and was resurected.

This North Carolina store preserves a historic moment in America's movement for racial equality.

The U.S. Navy’s preposterously detailed mini battleship took 77,000 hours to complete.

Turn around and stick your head between your legs for the best view of this tree-covered sandbar.

This former Texas landfill is flush with 300 million-year-old fossils, all fit for the taking.

Locals transformed this Canadian evergreen into a secret hangout with spectacular views of Vancouver's skyline.

A curious carving hides on a marble column in the Mosque-Cathedral of Córdoba.

A fairytale island floats in the middle of Italy's little-known Lake Orta.

Potato-peeling mannequins, Inca art, and a dangling tuber mobile help trace the history of fries at this Belgian museum.

The darkest building on Earth was built for the snow-white scenery of the 2018 Winter Olympics.

After Havre burned down, the best place to build was under the ashes.

A working ranch doubles as a sustainable hub for world-renowned classical music and large-scale sculptures.

Bioluminescence in the reefs of the Maldives causes the sea to glow like a starry night sky.

The fictional star of "Breaking Bad" is memorialized with a real-life gravestone in his hometown.

A whimsical village of unique treehouses resides in a Washington forest.

The traditional houses along the coast of this charming Japanese fishing village allow people to sleep above the sea.

At just six feet two inches deep, it is said by Guiness and Ripley to be the world’s narrowest freestanding office building.

Building owners can take out tiles for free at this repository for historic building materials.

A labyrinth of ancient tunnels hidden below the city holds the ruins of 2,500 years of history.

The steepest classic funicular in the world glides along a dizzying incline.