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

Frank Lloyd Wright built this suburban synagogue late in life, but it stands among his most iconic masterpieces.

This stately 19th century library pushed architectural boundaries at a time when the public library movement was just taking off.

A pyramid commemorates the birthplace of James Buchanan, the 15th president of the United States

Narrow gorges and deep pools created by long-ago glaciers.

The site of the little-known Pennsylvania battle that sparked the Seven Years' War.

In this cemetery stands the country's first public crematorium.

The first of Lancaster's "rural cemeteries."

Hundreds of protractors affixed to surfaces all over the city.

A pride of the state, this working museum crafts pottery mosaics in the style of Pennsylvania's earliest European settlers.

This roadside stand packs 300-plus varieties of tomatoes, from "Maiden's Fire" to "Kaleidoscopic Jewel."

America's smallest national park site is the former residence of exiled Polish national hero Thaddeus Kosciuszko.

The oldest surviving presidential residence in the United States.

One of Philadelphia's largest murals resides hidden under this bridge.

This dramatic rail curve was once the target of a failed Nazi attack.

One of the oldest of its kind.

A retired firefighter created this contraption so he and his family wouldn't die if accidentally buried alive.

Pennsylvania's highest point is spotted with boulders which were pushed to the surface by nothing but cold.

Steepest flood safety railway in the entire world.

Alexander Hamilton’s creation caused quite a bit of controversy.

The world's third-largest crystal sphere has sat in the Penn Museum since 1927 with the exception of one outlandish theft.

This stone tower marks a lookout point over the historic Washington Crossing, and maybe some buried treasure.

One of the U.S. Forest Service's only mansions is outfitted with a dinner table for floating food.

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