1. The Eye of the Sahara, Mauritania
This 25-mile-wide depression is reminiscent of a bull's-eye from the air. It's located in the middle of a flat and featureless area of Mauritanian desert. It was formed by wind erosion over the course of millions of years. The wind eroded various layers of sediment, quartzite and other rocks to give the Eye its appearance.
2. Socotra Archipelago, Yemen
The Socotra Archipelago has been isolated almost completely without interruption for millions of years, which has resulted in some bizarre instances of evolution. It is home to trees that ooze blood-red sap (pictured above), as well as others that are shaped like bottles. In addition, there are 180 bird and 700 plant and fauna species that aren't found anywhere else on earth.
3. Spotted Lake, British Columbia
This lake emerges during the summer when most of its water evaporates, leaving behind large concentrations of salt, titanium, calcium, sulfates, and other minerals that form a polka-dot pattern on the surface. In addition, the polka dots appear in different shades of green, yellow and brown circles. The lake is a sacred site to the First Nations of the Okanagan Valley.
4. Moeraki Boulders, New Zealand
Although they appear to be have been put there by giants, these enormous spherical structures are made up of masses of compacted sediment that was formed underground more than 50 million years ago. The eroding sand around them eventually led them to appear on the surface. They measure several feet across.
5. Silfra Rift, Iceland
This wondrous place allows you to swim and dive in a gigantic crack that represents the boundaries between two tectonic plates. The water is so clear in this location that divers report underwater visibility of up to 1,000 feet. It comes from melting glacial ice that takes over a century to reach the rift.
6. The Cave of the Crystals, Mexico
More than 1,000 feet underground in a working lead and silver mine, giant crystals of gypsum crisscross a cave, sprouting out at all angles. This cave was only discovered in 2000, and has to be navigated carefully, because temperatures can reach 150 degrees Fahrenheit. That's not to mention near 100% levels of humidity. Some of the crystals are four feet wide and 50 feet in length.
7. Waitomo Glowworm Caves, New Zealand
Bioluminescence is the ability of living organisms to illuminate themselves in the darkness. It's actually possible to take a ride through the cave system that these famous glowworms live in. As your eyes adjust to the darkness, they collectively begin to look like a turquoise starscape.
8. Chocolate Hills, The Philippines
On Bohol Island, there are some 2,000 symmetrically shaped hills that, on occasion, rise 400 feet above the surrounding farmland. The Chocolate Hills are actually made out of limestone, and are covered in grass. It's pretty obvious to see why they're called the Chocolate Hills, isn't it?
9. Asbyrgi Canyon, Iceland
Legend has it that this canyon was formed by the hoof of a Norse god's horse touching the ground, but a much more plausible explanation is that it was formed by glacial flooding between 3,000 and 10,000 years ago. The canyon is two miles long and half a mile wide, and is surrounded by cliffs that are more than 300 feet high.
10. Sahara el Beyda, Egypt
As you can imagine, the Sahara Desert isn't the most varied landscape in the world, but there are curious stone pillars that rise above the desert's sand in certain places. At Sahara el Beyda, you can see the sharper, whiter layers of sedimentary rocks peering through.
11. Lake Retba, Senegal
A particular kind of algae called Dunaliella Salina is the reason for this unusual lake's pinkish-red color. It also has extremely high salt content, which allows the algae to thrive and swimmers to float on its surface effortlessly.
12. Ice Towers of Mount Erebus, Antarctica
Mount Erebus is the world's most southerly active volcano. Due to Antarctica being so cold, escaping volcanic gas passes through caves and freezes, with some of it forming into chimney towers that can stand more than 60 feet high
Content source: Travel and Leisure
Image sources: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12