The perfectly named cave drop is the deepest in the continental United States, almost matching the height of Seattle’s Space Needle.

A 40-foot waterfall flows into this unique natural swimming hole.

A beach made of semi-precious green sand on the Big Island of Hawai'i.

A Bronze age settlement on the Greek island of Santorini might have been the inspiration for Plato's Atlantis.

This ancient statue of Dionysus lies unfinished and abandoned in one of Greece's oldest quarries.

Explore the largest pure gypsum deposit in the world, and go dune sledding while you're at it.

Under the right circumstances, this waterfall in Yosemite briefly turns a luminescent fiery orange.

An Italian crevasse filled with abandoned buildings gives visitors a look at the world without humans.

The only swimming pool listed on the National Register of Historic Places is emptied and refilled each day with naturally filtered water.

A 140-year-old castle with underground caves hidden in San Francisco.

This dramatic landscape hidden on the Isle of Skye looks as though you've stepped into the magical realm.

These remote Florida islands have a history of sea turtles and sunken treasures, and one of the world's largest coastal brick fortresses.

Remants of foundations, streets, and streetcar tracks inhabit the cliffs where a landslide occurred in 1929.

On Japan's Tashirojima Island, cats are king.

Dramatic river bend surrounds a natural red-rocked pedestal.

This jaw-dropping 19th-century bridge uses its reflection to form what appears to be a perfect circle.

The world's only museum devoted to the wonders of fluorescence.

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

This secluded aqua waterfall in the Grand Canyon is the perfect swimming hole, and the Havasupai tribe's fiercely protected natural wonder.

The mysterious, fantastical woodland inspiration for "The Lord of the Rings."

These fantastically named natural pools look like something out of a Scottish myth.

An exquisite tunnel of cascading flowers.

The sound of swaying stalks in this stunning grove has been named a governmentally recognized sound.

These old stone ruins in the Oregon wilderness were once bathrooms and are steeped in legends of murder.