The slate extracted from these Pennsylvania quarries was once hailed as the finest in the world.

What looks like a simple quaint estate in rural Pennsylvania was in the 18th century home to a small monastic community.

North America’s largest collection of horological devices and home to a colossal clock with a dizzying array of features.

The first of Lancaster's "rural cemeteries."

This splendid Versailles-inspired mansion has the largest French-style formal gardens in North America.

Descendants of this colonial Pennsylvania family still travel from far and wide to visit the 300-year-old home of their Quaker ancestors.

This collection of odd proofs of concept is like taking a walk through the imagination of a Victorian engineer.

A blend of art, antiquities, and Americana fill this museum, surrounded by whimsical, enchanting gardens.

These lush botanical gardens employ the most purrfect pest control force.

This palatial botanical garden is home to one of the largest pipe organs ever installed in a private residence, and a piece of Wood's cycad.

A larger-than-life statue of America's favorite sundae marks the place it was invented.

The ruined remains of a coal mining ghost town are hidden within the woods.

Memorializing an American tragedy of massive proportions.

Steepest flood safety railway in the entire world.

A field of nothing but boulders which resembles a giant's gravel driveway.

An Olympic hero stripped of his medals is buried in a town he never visited, which took his name after his death.

This jail which was in service for over a century is now open for curious visitors.

A museum dedicated to the history & joys of the trail & your best chance to see hikers throwing up ice cream.

The Cold War-era "underground Pentagon" is a sprawling subterranean hideaway for the Defense Department.

An almost life-sized elephant named Ms. Ellie greets visitors at this jumbo-themed museum.

One of the oldest Catholic churches in the U.S., situated just east of Gettysburg.

A diorama of the Civil War, fought by cats.

A dramatic, 360-degree recreation of Pickett's Charge in the Civil War.

Once the world's largest reinforced concrete structure, this abandoned bridge now beckons urban explorers.