This Florida sinkhole hides a rainforest-like micro-environment in its depths.

The scuba diving training facility was named for the steam that rises from the cave's chimney.

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

This homegrown adoption center offers a wonderland of feline companionship.

Better known as the "Body Farm," this unique research facility has been studying how human bodies break down since the 1980s.

Labor provided by Great Depression-era programs restored these 25,000 acres in Tennessee.

Mile-long cave system near Great Smoky Mountains.

This head-spinningly bizarre Depression-era art cave is wall-to-wall quartz and Jesus.