This 19th-century building inadvertently preserved the handprints of its builders within its walls.

Mile-long cave system near Great Smoky Mountains.

Less a museum than a bizarre fantasy world created by artists and engineers.

A still functioning vaudeville carousel that has operated for over a century boasts a colorful menagerie and past.

At the base of the Golden Gate Bridge, a small sign basically begs for a high-five.

A huge musical instrument played by the ocean.

Designed by famed architect Horace King.

One of the largest free-standing structures ever built, this dirigible hangar is now simply a giant skeleton.

A "gravitational anomaly" located in the redwood forests just outside of Santa Cruz, California.

Beneath the southern end of the Golden Gate Bridge is the “Gibraltar of the West Coast,” a fort built to protect the San Francisco Bay from naval attack.

Chevron maintains one “Standard” brand station per state so it doesn’t lose the trademark.

The former headquarters of history's oldest megacorporation.

This windmill has been grinding pigments for traditional paints for more than 200 years.

A Dutch clog company in the town of Zaandam loves the wooden shoes so much it made a museum for them.

The ruins of a medieval castle that once belonged to one of the most powerful families in the Netherlands.

A journey through 430 years of bulbiculture in the Netherlands.

For a moment, you could think there are two identical communication towers in a row, but one of them is made out of PVC.

A nourishing complex of found object art, paintings, and sculptures that celebrate key figures in Black history.

The oldest continuously operating pharmacy in Europe.

Walk along the medieval fortifications that have been protecting Tallinn since the 14th century.

The Guardian of Tallinn.

During the Soviet era, the spire of this longstanding church was used as a radio transmission tower.

The mysterious 855-foot zigzagging stone wall has been baffling people for centuries.

These enormous, stern-faced statues greet visitors with lanterns, and sometimes costumes.