If astronomy had a ghost, it would look like this observatory.

A phenomenal assembly of pueblos in New Mexico is the most complete example of ancient ruins north of the border.

These pretty kitties killed and ate as many as 135 railway workers.

Try not to get slimed in Tribeca.

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

A priceless collection of the Nation's cryptologic history.

A museum dedicated to exhibiting remarkable outsider art.

The last remaining relic of San Francisco's glittering 1915 Panama Pacific Exposition.

Not merely a museum – but a whirring powerhouse that offers a subterranean peek into the heart and soul of cable car operations.

San Francisco's newly reopened hands-on science museum.

An amazing collection of fantastic reptiles, amphibians, spiders, and insects.

An extensive collection of ancient Egyptian artifacts and mummies.

A store that sells all manner of bones, insects, and animal curiosities.

The world's third-largest scale model of the planets.

The world's largest anatomically accurate brain sculpture.

This is not your typical jungle gym.

Curious rock formations in a tiny Kansas state park.

Strange red rock formations that have been attributed to a higher power for hundreds of years.

The first declared National Monument in the United States.

The world's largest piece of copyrighted artwork.

Ice cream stand, snack bar, and time capsule of milk conveyance.

This landmark cemetery in Boston was created more than 300 years ago.

What was once a true peninsula has now been filled in, causing the water to recede and leaving many streetside "waterfronts" and landlocked "islands."

The world's largest mountain carving could fit all of Mount Rushmore inside it many times over.