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

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

An underwater city for the dead.

In the middle of a suburban Denver neighborhood is a cave that once provided solace for a prominent Ute chief and his family.

A stark reminder of the huge nuclear weapons plant that once stood on the site and its effect on the surrounding area.

This hot dog-shaped diner has moved all around Colorado, never been to New York.

Colorado's only true geyser is hidden within the San Juan National Forest.

The scene of one of the darkest moments in American labor history has been left essentially untouched since the tragedy.

This super steep hike ascends 2,000 feet in less than a mile.

The world's largest carnivore sanctuary is home to over 450 meat-eating rescues.

A little-known hot spring haven right below the highway.

The superstar of Cold War nuclear bunkers has been featured in countless films but is now barely operational.

The highest bridge in America was built for an almost unnervingly small amount of money.

The largest self-built castle in the U.S., six decades in the making.

Crystal clear lake with a shoreline of travertine located in a Colorado canyon.

Wondrous sandstone hoodoos where Native Americans collected clay for pottery, 9,000 years ago.

You don't have to visit the deep blue sea to see these majestic creatures swimming wild and free.

These hellish-looking cliffs in the Canadian Arctic have been burning for centuries.

Saved by a logger, this Douglas fir is one of the last great old-growth trees in Canada.

The statue of the famous elephant who was the original source of the word "jumbo".

One of Mother Nature’s geological gems, home to many prehistoric fossils.

Historic site where Native American hunters once trapped and killed buffalo.

This sprawling collection hides many charms.

Unlike many reclaimed, abandoned mines, this Canadian cave system is still just a dangerous maze.