This super steep hike ascends 2,000 feet in less than a mile.

This charming colonial alleyway is one of the oldest continuously used residential streets in the U.S.

The famous facade of Grand Central Terminal hides a regulation tennis court—and it's not the first one.

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

Whisper secrets in a busy station only to be heard on the other side of this acoustic arch.

The longest continuous lava tube in the continental U.S. offers 2.5 miles of dark explorations for the adventurous.

A roaring, awe-inspiring double cascade of icy water flows through woodland Oregon like something out of a Tolkien novel.

A Roman-style column in Oregon hides a spiral staircase inside.

A massive sea stack famous for its appearance in The Goonies.

This striking art museum holds an amazing series of curiosity cabinets.

A factory in Milwaukee where poop is reclaimed… and recycled.

Thanks to a quirk of elevation this gift shop produces magic doughnuts that are found nowhere else on Earth.

The Denver airport is guarded by a 32-foot-tall sculpture of a demonic horse.

At this Denver landmark, the meals are compulsory, the sopapillas are complimentary, and the insanity is everywhere.

A place to eat for on-the-run agents and espionage enthusiasts.

Each year these high desert hills are absolutely covered with poppy flowers in a surreal show of nature.

Quite simply the largest tree in the world (by volume).

The high point on the 16th president's eponymous roadway is marked by a massive version of his head.

100-year-old shipwreck you can walk up to at low tide.

Strange red rock formations that have been attributed to a higher power for hundreds of years.

The highest paved road in North America winds its way up Mount Blue Sky in Colorado to an altitude of 14,130 feet above sea level.

The superstar of Cold War nuclear bunkers has been featured in countless films but is now barely operational.

Air Force Academy Chapel made of 100 identical tetrahedrons works to inspire those of all religions.

The remains of the dam that unleashed a 15-foot wall of water on Denver.