The internal railway of one of the biggest steel plants in America has been transformed into a linear park with unique industrial views.

During World War II, Austria's oldest salt mine was used to store thousands of pieces of stolen artwork.

A small cave hidden deep within the Jenny Jump State Forest.

Take an underground boat ride through a former hydraulic raceway that was built in the late 19th century.

A mixture of strange symbols, ciphers, words and cryptograms carved in 1876 remain unsolved to this day.

A reservation-only highland forest reserve of endangered Pinsapar firs stands above a village in Andalucía.

On the outskirts of San Antonio, a small bridge is said to be the home of a mysterious local legend known as the "Donkey Lady."

California's largest steel arch bridge.

Will Geer's outdoor theater started as a mountain retreat for actors, musicians, and other artists who were blacklisted during the Red Scare.

The longest step street in the city.

An interesting look into 18th-century American history.

An institution dedicated to the towering buildings that make up skylines in New York City and around the world.

One of the country's best automotive museums and home to one of the first motor vehicles.

Believed to be the first museum dedicated to the films in the world.

The highest bridge in Myanmar was once the tallest railway bridge in the world.

Built in the 1920s, this co-op in the Bronx feels more like an Italian villa than a typical New York apartment building.

The oldest private residence in New York City.

The only subway station in the city that still makes use of gap fillers.

A collection of vehicles across American military history.

A natural sandstone bridge hidden in the Sewanee forest.

An amazing example of Federal-period architecture, truly unique to this region of the state.

Preserving the memory of the narrow railroads that once crisscrossed the state of Maine.

A shoreline exhibit describing the disastrous first attempt by the French to colonize North America.

Catch a ride through the Pennsylvania countryside on this historic narrow-gauge railroad.