A tiny red pebble marks what may be the quietest outdoor spot in the United States.

A surreal landscape where fanged rocks rise from the ground and the ocean feels like a great mystery.

A whimsical village of unique treehouses resides in a Washington forest.

The longest continuous lava tube in the continental U.S. offers 2.5 miles of dark explorations for the adventurous.

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

On the Oregon coast there is a natural hole that seems to be draining the sea.

A county library in rural Ohio houses one of the finest mineral collections in the world.

Half of a waterfall goes into the river while the other half seems to disappear.

These Great Lakes sea caves accessible by boat in the summer turn into temples of ice reachable by foot in the winter.

This natural sea cave hides a small wonderland of natural turquoise beauty.

Strange physical sensations and optical contradictions keep visitors coming back for more.

This shallow cave got its name from copious amount of human bones found inside.

A stunning, two-tiered waterfall made famous by poets, artists and the legend of a ghost dog.

This natural spring not only claims to heal the wounded but it has also been willed to God.

Discovered by a soldier during the Revolutionary War, these springs helped create an iconic South Carolina ginger ale.

Once part of a dam servicing an early 19th century grist mill, the tucked-way falls are a tricky-to-find urban oasis.

Who needs fancy modern water slides when this giant North Carolina rock works just as well?

The mysterious wonder of an underground waterfall is illuminated by multicolored lights.

Enormous lake at the bottom of a unique cave system.

Visit this playground of waterfalls, caves and sinkholes.

This freshwater spring fills with 10,000 gallons of water per minute.

This large midwestern cavern features impressive rock formations and an underground waterfall.

Rare recess caves fill this unbelievably beautiful Ohio park.

This pebble beach is so beautiful that taking its rocks is against the law.