Once decrepit and slated for demolition, now one of the longest pedestrian bridges in the world.

More than five miles of underground passageways.

Live long and prosper in Tennessee.

A propulsion engine testbed that paved the way for the Space Shuttle launch sits without recognition at this rocket center.

It may look like no more than a full-scale model, but every part of this full Space Shuttle stack had a working role in aviation history.

One of the few surviving "Wigwam"-themed motels.

Prehistoric animals decorate this popular outdoor park.

The world's longest known cave system.

This simple, broken column marks the final resting place of one of America's most famous explorers.

This replica of the Greek structure is in the heart of Nashville.