A mysterious castle built as a monument to lost love.

Where manatees are the snowbird vacationers in these balmy Florida springs.

An underwater city for the dead.

The only swimming pool listed on the National Register of Historic Places is emptied and refilled each day with naturally filtered water.

These remote Florida islands have a history of sea turtles and sunken treasures, and one of the world's largest coastal brick fortresses.

Enormous lake at the bottom of a unique cave system.

For two weeks every June, fireflies in the Smoky Mountains perform an astonishing light show.

Mile-long cave system near Great Smoky Mountains.

This former maximum-security prison is creepy, sobering, and supposedly haunted.

One of the Cemestos prefab homes built to secretly house thousands of Manhattan Project workers.

A bronze sculpture honors the 12 black students who attended the first integrated public high school in the segregated South.