The last remnants of Fort Pitt also hold the distinction of being the oldest structure west of the Allegheny Mountains.

One of the steepest streets in the United States makes an intriguing challenge for cyclists.

A tradition unlike any other, this marks the site of the annual Groundhog's Day tradition.

Locals call this magical moss-covered walkway the "Emerald Path."

"Where the ducks walk on fish."

A living maritime paradox still floats in the same lake where it was built and resurrected... or was it?

A quirky collection of outsider art made from automobile parts.

The only statue of its kind to commemorate Washington's beginnings as an officer of the British Colonial Militia.

The Pennsylvania landscape depicted by a quarter mile of mosaics made from used road signs.

Priceless space junk on display in front of a local Dairy Queen.

The oldest continually operating golf course in the United States.

An abandoned railroad tunnel transformed into a creepy path for hikers and cyclists.

For decades, it has disappeared and reappeared as water levels rise and fall.

The site of America's first commercial oil well essentially disappeared after the town went bust.

Where the oil industry began.

A dazzling display of lights and crystals.

A rotating cast of guys and dolls in front of a Washington, D.C. building.

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

The only way to see Pittsburgh is from the top of this lookout point, just like the ancient members of the native peoples did.

This lonely waterfront memorial to the men of the Titanic was erected by the "Women of America."

A hidden gem on the lawn of the U.S. Capitol Building designed by landscape architect Frederick Law Olmsted.

A cavernous three-story, 43,800-square-foot basement that was forgotten about for 60 years.

The tunnel under the Capitol Building where Congress takes out its trash.

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