A crumbling hospital from the 1850s on Roosevelt Island.

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

One of the largest trees of its kind in California.

An extraordinarily ornate museum in San Diego holds wondrous anthropological treasures.

Breathtaking and huge 430 year old maps of Italy.

Six tiny houses built for working class people form the largest intentional cluster of Wright homes anywhere.

A unique botanical garden housed in three giant geodesic domes.

An off-the-beaten-path place to literally hang beneath Milwaukee's Holton Street Bridge.

There’s a hidden military meme engraved on the World War II Memorial.

Decades before the scandal, this staircase on the river was a literal "water gate."

The 5.5-mile ring of steel posts around the Capitol Building is one of the largest (and most uniform) of its kind in the world.

The walls of the iconic dome are hollow and have a secret stairway.

Members of Congress have traveled between the buildings on Capitol Hill for a century hidden from tourists, press, and storm clouds.

Rumor has it the uncarved lump behind the three famous suffragists is reserved for the first woman president.

One of the most influential presidents in U.S. history wanted only this plain, elegant monument as his lasting memorial.

Look closely and you’ll notice that the color changes a third of the way up the tower.

This working class sculpture pounds his hammer all the livelong day.

A wall of chewing gum moonlights as collective art.

A giant Troll lurks under one of Seattle's oldest bridges.

These pretty kitties killed and ate as many as 135 railway workers.

Years of archaeology, just chillin' by the water cooler.

Each of these gorgeous, intricately decorated rooms is painstakingly crafted to the scale of 1 inch: 1 foot.

Once at the center of U.S. finance, the historic Trading Room was meticulously recreated piece by piece and rebuilt in the Art Institute.

The home of 1.5 million wood letters for printing is still a functioning workshop.