Earth's tallest volcano is sacred to Native Hawaiians, and home to a dozen world-class observatories.

With well over 130 falls and cascades to brag about, Hamilton, Ontario has earned its stripes as the waterfall capital of the world.

The world's highest and most dangerous infinity pool lies at the precipice of Victoria Falls.

An abandoned set from the 1980 film "Popeye," claimed and repurposed as a theme park by creative locals.

This giant boulder is pinched over a 1000-meter abyss by two mountains.

Living trees form the structure of an open-air palace.

Once the path of a railway tunnel, now home to thousands of glowing insects.

If a glacial river suddenly diving into a sheer chasm via a dramatic, multi-stage waterfall isn't peak Iceland, it's certainly close.

The mysterious megaliths have enchanted and intrigued visitors for thousands of years.

World's largest cave was only discovered in 1991, and now offers tours to the public.

This vertical pinnacle in China was the inspiration for the floating mountains in the movie “Avatar.”

This lovely little bridge hidden in a Switzerland gorge is essentially a fairytale.

Hundreds of stone stairs and a winding medieval bridge connect this haunting Spanish island to the mainland.

In a 345-million-year-old cave that's 200 feet underground, dinner awaits.

This amazing pedestrian suspension bridge in the Swiss Alps would give Indiana Jones nightmares.

Caves famous for the dragon-slaying saint who lived there.

This domed temple was built in a hidden cave mouth as a refuge for sinners seeking absolution.

Natural time capsule containing an alien ecosystem.

The highest point in Washington state is a volcano covered in glaciers.

Sacked by Vikings, blessed by William the Conqueror, dealt a fatal blow during the French Revolution—these ruins have seen it all.

This Oregon farm is dedicated to teaching people the professional art of tree climbing.

This funicular railway rumbles along for a mile up the nearly vertical face of Chattanooga’s Lookout Mountain.

Hidden in a secluded Greek cove is a pristine beach marred only by the rusting smuggler's hulk stranded on its shores.

One of the most unusual geological features, recognizable from a dozen hit movies.