This historical air terminal in Houston is slowly becoming an aviation museum dedicated to the city's aeronautical history.

The remains of Martha, the last known passenger pigeon, serve as a tool to educate about conservation.

Largest Roman Catholic church in North America.

These massive mitts are made of 30 tons of devotional bronze.

The semi-reclaimed ruins of this canal were once part of an ambitious plan to reroute the mighty potomac.

The ghostly remains of an accidental sea.

Some of the tallest ancient American ruins continue to inspire awe and curiosity.

See massive fossils that are over 200 million years old in northeastern Arizona.

The second-largest cave chamber in the world was discovered in 1898 by a 16-year-old and a friend known as "Pothead."

The site of Billy the Kid’s most famous escape and the end to the Lincoln County War.

Explore the largest pure gypsum deposit in the world, and go dune sledding while you're at it.

Natural catch-basin rocks covered in thousands of drawings spanning many millennia.

A hillbilly theme park that proved so unpopular the land wouldn't even sell on eBay after it closed.

A museum honoring Oklahoma military service, where you can look into Hitler's mirror and see a Mickey Mouse gas mask.

An oil baron's wild paradise and the winner of an ill-fated air race.

Nature's biggest mammal swims in landlocked Oklahoma.

The legend of a local monster still haunts this small town.

The world's tallest statue of an American hero.

Official museum, hall of fame, and repository of the Texas Rangers.

Modern technology and live displays tell the story of the Pacific during WWII for the Internet generation.

Three hundred years of preserved Spanish colonial history in San Antonio.