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

The world's largest occupied bat houses hold hundreds of thousands of flying mammals.

Over 12,500 words are scrawled across each room of this historic plantation house and no one knows why.

Despite being burnt down multiple times, the ruins of this South Carolina church are still standing.

North America's oldest authentic African Village.

One of the oldest living oak trees in the Southeast.

I-95's Tijuana-style celebration of kitsch at the Carolina border.

The literary king of the Jazz Age was born in this lovely Minnesota home which still honors his legacy.

This sky-high radio mast is formerly the tallest man-made structure in the world.

The world's largest Holstein cow.

The first declared National Monument in the United States.

This playground sculpture of an icon from the past is dedicated to the children of the future.

Stroll through a wonderland of stupendous moss-covered trees.

A roaring, awe-inspiring double cascade of icy water flows through woodland Oregon like something out of a Tolkien novel.

The deepest lake in the United States, and once the site of epic destruction that lives on in legends.

Quite simply the largest tree in the world (by volume).

Thousands of turbines whir at at the origin of North American wind power.

Giant, natural amphitheaters made of delicate geological formations called "hoodoos."

This raised bulls-eye visible from space was the subject of an intense geologic controversy.

The spot in the Mile-High City that's exactly 5,280 feet above sea level (at least for now).

Community bookshelf of 25-foot-tall book spines.

Once one of the world's great cities, Cahokia was a place of religious worship, trade and mass human sacrifice before being mysteriously abandoned.

The Old Courthouse takes visitors on a captivating trip through St. Louis' timeline.

The world's longest known cave system.