Mount Bromo is perhaps the most well-known volcano in East Java's Bromo Tengger Semeru National Park, thanks to its accessibility and epic sunrise views.

This salt lake sure is beautiful to look at, but its hellish 120-degree temperatures and dangerously low pH levels make it a less-than-ideal vacation spot. There is one major upside: The surplus of scarlet-hued algae attracts millions of flamingos, making the area one of the species' major breeding grounds.

Leave it to New Zealand to make even worms look beautiful. The Waitomo Caves hold thousands of bioluminescent larvae that leave long strings of mucus (sounds gross, looks dazzling) and glow like a subterranean Milky Way.

Red sand dunes and skeletal trees make Namibia the closest thing we have to Mars on Earth.

Scenic might be an understatement: This 100-square-mile attraction contains thousands of sandstone pillars that are nature's version of skyscrapers—some even stretch taller than the Empire State Building's midpoint. It's no wonder this site was a major inspiration for the world of Pandora in Avatar.

Vietnam's Hang Son Doong, the largest cave in the world, could hold an entire city block of Manhattan—including 40-story skyscrapers. It has its own lush vegetation where sunlight filters in from sinkholes above, and clouds even form near the ceiling when moisture condenses there. In other words, it's practically its own little world lurking under the earth's surface.

The glacial lake of Jökulsárlón and its frozen beach are considered a natural wonder of Iceland, with black volcanic sands providing a stark backdrop for the chunks of ice that wash ashore.

With UFO-like dragon's blood trees as its most notable feature, the island of Socotra looks like it was transported to Earth from a distant planet.

As its name suggests, the largest hot spring in the United States is essentially a rainbow ring of vibrant colors.

This cavernous cenote with double entry points—hence the moniker "Two Eyes"—is so incredible it was featured in the IMAX flick Journey Into Amazing Caves and an episode of Discovery Channel's Planet Earth. It's perfect for snorkelers, experienced scuba divers, and daredevils willing to surface in the system's bat cave.

A kind of geological wonderland of salt formations, acidic hot springs, and gas geysers, this visually stunning hydrothermal field vies for the title of world’s hottest spot with average summer highs reportedly hitting up to 114°.

The 13,800-foot climb from Hilo's beaches to the moonscape at the summit of Mauna Kea isn’t for the faint of heart. It is one of the longest sustained climbs on Earth, but it's worth it to view the world as a land above the clouds.

Have you ever dreamed of exploring the moon? A trip to Valle de la Luna in Chile’s Atacama Desert is a much shorter flight. Years of erosion have left behind jagged peaks, dry riverbeds, and a landscape startlingly similar to that of our favorite celestial body's.

The geography of Brazil's Lencois Maranhenses National Park is like nothing else on Earth. The rainy season (around early June) fills every trough with water and the world becomes an M. C. Escher print: It is either a drowned desert or a sandy lake, depending on how the mind's eye frames what it is seeing.

The landscape of the White Desert can be deceiving: What first appears to be a cool, snowy landscape is actually a mind-bendingly hot region of western Egypt. The desert is known for its wind-shaped chalk rock formations, which often resemble giant mushroom clouds frozen in time.