Cathedral carved out of salt, located a mile below the Earth's surface.

Funded by John D. Rockefeller, this is one of the earliest, and most beautiful, shopping arcades in America.

Cleveland's giant "free" stamp is a nod to the Civil War, but was misinterpreted for years.

This stuffed pigeon of war had the very serious name "John Silver" until he lost a leg in battle.

You can walk through the first Boeing Air Force One, which famously carried JFK's casket from Dallas back to D.C.

Eerie ruins of an abandoned medieval fishing village crumble atop an unforgiving stretch of earth.

Now abandoned, the first public health hospital in the U.S. saw more than one million immigrants from around the world.

A vista of the city and sea from atop the little-known viewing deck on an unassuming Columbus statue.

The massive machine creates cracking displays of indoor lightning.

Did Inca children also slide down these smooth rocky slopes above Cusco?

The one-stop shop for all of your superhero (or evil arch-nemesis) needs.

The smallest island in Manhattan is a manmade landfill dominated by a Buddhist peace arch.

This whimsical group of statues is a favorite of children who love to climb all over Lewis Carroll's beloved characters.

Mrs. Mallard and her brood are a beloved fixture in Boston Public Garden.

Celebrating the greatest pugilists the world has ever known.

These mystical miniature houses bring a touch of magic to the New Jersey woods.

A popular European tradition makes its way to the states on one of America's most famous bridges.

This nearly invisible wire transforms much of the city into one big, symbolic home on the holy day.

Hundreds of glow-in-the-dark objects light up a museum in a historic zinc mine.

This abandoned radar station from the Cold War era now only broadcasts a seriously ominous air of isolation.

An abandoned asylum incorporated into a college campus.

Ninety feet off the valley floor is an ancient dwelling put under protection of the U.S. government by Teddy Roosevelt.

Genesis of modern hydroelectric power.

Niagara Falls holds a special place in Nikola Tesla's history, so they put a statue on it.