400 million-year old limestone caverns nestled in the Ozarks served as shelter and a hideout for cultures throughout North American history.

What was once a presidential estate is now an exotic menagerie and home to the Budweiser Clydesdales.

One of the world's earliest skyscrapers.

The Old Courthouse takes visitors on a captivating trip through St. Louis' timeline.

Speak to a companion on the other side of the room loud and clear through this architectural anomaly.

One of few surviving standpipe water towers in the U.S.

A commemoration of over 150 of St. Louis's favorite sons and daughters.

This titanic oil company sign is a reminder of the Americana boom of the 1970s and also its commoditization.

What was meant to be a temporary exhibit is now a permanent fixture at the St. Louis Zoo filled with beautiful birds.

When you visit his grave, be sure to rub the Great Emancipator's nose for good luck.

The original vault that held the president's remains still stands, empty, not far from where he was finally buried.

Once known as the Illinois Asylum for the Incurable Insane.

America's most famous museum of medical oddities is home to the remains of Albert Einstein's brain.

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

The largest university building in the West is a gothic masterpiece containing dozens of theme rooms based on different countries.

A model of a dinosaur that was named for Andrew Carnegie stands outside the museum that also bears his name.

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

This extravagant Art Nouveau rest stop features a million-dollar view of the Columbia River.

You might recognize this historic Oregon mansion from its appearance in 'The Goonies.'

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

The only royal palace on U.S. soil has been a territorial capitol, a military headquarters, and a prison for a queen.

Once the site of the Hawaiian monarchy, this building was originally designed as a palace.

The world's longest outdoor covered escalator system transports commuters through Hong Kong's hilly terrain.

These pastel-colored homes were built when the island of Macau was a Portuguese colony.