Martin Bricelj Baraga's monolithic sculpture measures the blueness of the sky, and changes color to match it.

This chain of artificial lakes was an ideal test ground for the aircraft that would carry the "bouncing bombs" used by the WWII "Dambusters" squad.

The first presidential bomb shelter was located in an old vault under the Treasury, connected to the White House via tunnel.

A cave in southern Italy adorned with thousand-year-old Biblical frescoes existed in obscurity until fairly recently.

The preserved arm of a third-century sorcerer is believed to have the power to lift curses and spells.

For 150 years one family has been producing the iconic hot sauce on a bayou island made of salt.

Neon signs that grace the windows of Bergdorf Goodman's and Tiffany & Co. come from this studio in Brooklyn.

The world's oldest Jewish library was founded by Sephardic Jews in 17th century Amsterdam.

Statues of Ramona Quimby, Henry Huggins, and Ribsy the dog in the park where their adventures "really happened."

This lake in northwest Iran has started turning from green to red more frequently than scientists are comfortable with.

The largest retailer of seashells in the world.

One of the last Jazz Age "Wonder Theaters" in New York City.

The hollow trunk of this 650-year-old tree was used as a hideout by two Jewish brothers during World War II.

An institution dedicated to curiosity, logic, riddles, and Mongolia's long history of puzzles.

This long line of cement defensive wedges is named after the famous chocolate bar for obvious reasons.

This tiny museum's sizable collection is jammed into a former underground public toilet.

What might look like a cliffside sacrificial altar at first glance is actually a stone compass pointing to cities and lighthouses all around the world.

This abandoned school has had many lives since the early 1900s, and all of them doomed.

About 80% of all U.S. avocados are descendants of Rudolph Hass's glorious tree.

This network of tunnels housed an entire village for years, and even had a hall for screening movies.

This poor little statue is the most vandalized memorial in Washington.

A Himalayan monastery claims to have a piece of a centuries-old abominable snowman.

Small teepee-like houses built for TB patients have become sheds, studios, and bus stops around Colorado Springs.

A subterranean shelter remains intact under a busy Paris railway station.