Frank Lloyd Wright's most iconic home dangles over a Pennsylvania waterfall.

There are more than 4 million bricks inside this unofficial Lego museum in a former middle school.

Rows of 19th-century brick ovens used to process coal into coke form the center of a wooded park.

The universally beloved children's television figure is interred on a high hilltop in one of western Pennsylvania's oldest cemeteries.

A museum commemorating the Donora Smog, which killed 20 people in October 1948 and sparked national outrage over air pollution.

Each step is a mere four inches tall, said to be measured by the stride of a woman wearing a hobble skirt.

This California artist's front yard acts as a gallery for his unique, scrap metal animal sculptures.

Housing the history of a small Ohio town that is known to some as the pottery capital of the United States.

After covering almost 1.5 billion acres, the survey's still not finished.

This icon of the Atomic Age now lays dormant.

A preserved 18th century homestead in Western Pennsylvania marks the spot where the Whiskey Rebellion began.

This eccentric mansion museum holds a impressive collection of rare and automatic instruments.

The last street in Pittsburgh that's paved with wood.

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

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

Hundreds of protractors affixed to surfaces all over the city.

An imposing pair of sphinxes stand guard outside this Egyptian Revival tomb.

The legacy of baseball great Roberto Clemente is preserved in a retired Pittsburgh fire station.

The United States’s oldest funicular railway glides up and down a steep Pittsburgh street.

Its vintage camera collection gives a snapshot of the past as viewed through a photographic lens.

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

This spot memorializes one of the greatest plays in NFL history, unless you happen to be a Raiders fan.

A stone arch leads to a cavernous 1930s spring house tucked away in the Pennsylvania woods.

The tallest outdoor elevator in Europe rockets passengers on a dizzyingly precarious ride to the top of a mountain.