In the midst of the vast, vacant Sahara desert, just outside of Ouadane, Mauritania, lies a 30-mile wide geological oddity known the Richat Structure, sometimes called the “Eye of Africa.” From space, this natural curiosity forms a distinct and unmistakable bulls-eye that once served as a geographical landmark for early astronauts as they passed over the Sahara.
Once thought to be an impact crater due to its circularity, the unusual formation is now widely believed to have been caused by the erosion of what was once a geological dome. Over time, desert weather has caused the dome to gradually shed layers, resulting in the structure’s remarkable flatness.
Grüner See (Green Lake) is a lake in Styria, Austria in a village named Tragöß. The lake is surrounded by the Hochschwab Mountains and forests. The name "Green Lake" originated because of its emerald-green water. The clean and clear water comes from the snowmelt from the Karst mountains and has a temperature of 6–7 °C (43–45 °F). During winter, the lake is only 1–2 m (3–7 ft) deep and the surrounding area is used as a county park.
However, in spring, when the temperature rises and snow melts, the basin of land below the mountains fills with water. The lake reaches its maximum depth of around 12 m (39 ft) from mid-May to June and is claimed to look the most beautiful at this time. In July, the water begins to recede.
Salar de Uyuni, amid the Andes in southwest Bolivia, is the world’s largest salt flat. It’s the legacy of a prehistoric lake that went dry, leaving behind a desert-like nearly 11,000-sq.-km. landscape of bright-white salt, rock formations, and cacti-studded islands. Its otherworldly expanse can be observed from central Incahuasi Island. Though wildlife is rare in this unique ecosystem, it harbors many pink flamingos.
Easter Island (Rapa Nui: Rapa Nui, Spanish: Isla de Pascua) is a Chilean island in the southeastern Pacific Ocean, at the southeasternmost point of the Polynesian Triangle in Oceania. Easter Island is most famous for its nearly 1,000 extant monumental statues, called moai, created by the early Rapa Nui people. In 1995, UNESCO named Easter Island a World Heritage Site, with much of the island protected within Rapa Nui National Park.
It is believed that Easter Island's Polynesian inhabitants arrived on Easter Island sometime near 1200 AD. They created a thriving and industrious culture, as evidenced by the island's numerous enormous stone moai and other artifacts. However, land clearing for cultivation and the introduction of the Polynesian rat led to gradual deforestation. By the time of European arrival in 1722, the island's population was estimated to be 2,000–3,000. European diseases, Peruvian slave-raiding expeditions in the 1860s, and emigration to other islands, e.g. Tahiti, further depleted the population, reducing it to a low of 111 native inhabitants in 1877.