An 18th-century Spanish watchtower made entirely of seashell and concrete.

The unique collection includes bronze cast handprints of some of America's most famous astronauts.

Town of spiritualists and mediums in Florida.

The world's largest private aircraft collection.

After the attack on Pearl Harbor, rocks and fossils from every U.S. state were collected into a pyramid of national unity.

A 1950s eccentric's vision of Eden preserved as a hiking trail.

One of only two pod-shaped homes designed by Frank Lloyd Wright.

This historic crypt was said to have been designed and built by the very person who is buried inside of it.

This historic headstone is said to mark the final resting place of a doubly-dead white witch.

This sidewalk monument honors more than 50 civil rights activists who helped change the face of America.

The highest point in Washington state is a volcano covered in glaciers.