1. Glowworm Caves in Waitomo, New Zealand
A species of glowworm native only to New Zealand dwell in the ceilings of these caves, resulting in a starlit canopy effect.
2. Marble Caves in Lago General Carrera, Chile
Six thousand years of gentle waves have carved winding tunnels through this boulder, revealing a sapphire-and-emerald marble design.
3. Mendenhall Ice Caves of Juneau in Alaska, United States
This cave sits beneath the Mendenhall Glacier, so the translucent blue ceiling is formed entirely by ice.
4. Fingal’s Cave on the island of Staffa in Scotland
The strange, geometric rock formations that make up this cave were actually caused by lava flow.
5. Ice caves in Vatnajokull, Iceland
These ice caves are inside an active glacier, so they're constantly in a state of change.
6. Stephen's Gap in Alabama, United States
Stephen's Gap is a vertical cave so when light pours in from the ceiling the effect is even more dramatic.
7. Sea caves in Algarve, Portugal
Much of the Algarve coastline is populated with these limestone caves and grottos.
8. Baatara Gorge Waterfall in Tannourine, Lebanon
You can view the 800 foot waterfall from a natural bridge that span the width of the pit.
9. Melissani Cave in Kefalonia, Greece
In Greek mythology, the sky-blue waters of Melissani were home to the nymphs, or nature fairies.
10. Carlsbad Caverns in New Mexico, United States
The Carlsbad Cavern is home to The Big Room, a natural limestone chamber that spans over 4,000 feet.
11. Minnehaha Falls Cave in Minnesota, United States
This seasonal cave only occurs when temperatures drop low enough to freeze the Minnehaha Waterfall mid-cascade.
12. The Reed Flute Cave in in Guangxi, China
These caverns are over 180 million years old and are still a popular tourist attraction in China.
13. Antelope Canyon in Arizona, United States
Years and years of flash floods carved a narrow passage through rock to create this brush-stroked canyon.
14. Eisriesenwelt Cave in Werfen, Austria
Eisriesenwelt translates to "world of ice giants" in German, which is a fitting name given that Eisriesenwelt is the largest ice cave in the world.
15. Cenotes in Yucatán Peninsula, Mexico
These natural sinkholes may have been used by the Mayans for sacrificial offerings many years ago.
16. Son Doong Cave in Quang Binh Province, Vietnam
In 2009 Son Doong became the world's largest known cave. One of its chambers is over three miles long.
17. Enchanted Well at Chapada Diamantina in Bahia, Brazil
Both gold and diamonds have been found in the clear waters of the Enchanted Well.
18. The Cave of Giant Crystals in Naica, Mexico
Some of the largest natural crystals in the world have been found in this cave, but the extreme temperatures (up to 136 degrees) make it difficult for humans to explore the cave at length.
19. Ice Cave in Kamchatka Peninsula, Russia
The thin ceiling of this ice cave allows light (and color) to penetrate its rooms.