A portal into the bricked up canal that runs through the heart of Washington D.C.

Daredevil repair workers can worm their way out the access hatch, loop ropes over the apex and rappel down the monument.

The U.S. Supreme Court's secret Cold War relocation facility in the mountains of North Carolina.

This futuristic airport terminal was abandoned for decades before reopening as a hotel—with a vintage plane of its own parked out back.

At 135 years old and counting, this historic print shop is heaven for poster nerds and music buffs.

A local dialect born in the late 19th century is only spoken in this isolated California valley.

This small hut in the middle of a parking lot was once the wooded sanctuary of the 'Hermit of Montrose.'

This beautifully designed star-shaped fort was the premier defense system of the late 1500s.

When Motown musicians came to Nashville in the 1960s they stayed at this historic record-pressing company because hotels wouldn't host them.

This Industrial Age architectural and engineering gem helps visitors and residents alike traverse Lisbon, “The City of Seven Hills.”

Georges Seurat’s pointillist masterpiece has been recreated in Ohio in topiary form.

While many places make the claim, the Library of Congress says this restaurant is the birthplace of the hamburger.

Yale University's home for rare works, including the mysterious Voynich Manuscript.

Birthplace of the "Cat in the Cradle" and a cluster of iconic, original windmills that let the Dutch tame the seas.

The perfectly preserved underground rooms where Churchill plotted the war against Germany.

Crumbling Kennedys and a decaying Tecumseh are just some of the haunting remains of one man's cement art trail.

This 4,000-foot-diameter hole is touted as "the most well known, best preserved meteorite crater on Earth."

Detroit housing collective working to create an "environment for revolutionary change."

The small cave that housed Tennessee's "first citizen."

This simple, broken column marks the final resting place of one of America's most famous explorers.

Golden Gate Park's historic collection of plants.

This Costa Rican chapel is the most metal church in the world, literally.

The first full-scale tunnel built in America is short but scenic.

One of the Seven Wonders of the Modern World holds the world's tallest metal staircase.