While some optical illusions have gone viral and stumped the internet, others you'll only see when you explore the outdoors.
From an underwater waterfall in the Indian Ocean to a surrealist scene in Namibia, we rounded up 12 naturally occurring illusions and optical phenomena that will make you do a double take.
Take a closer look below and find out how these illusions are created.
This may look like a surrealist painting, but it's actually a photo of Deadvlei in Namibia.
Located inside Namib-Naukluft National Park, Deadvlei is a claypan dotted with many long-dead camel thorn trees, which have not yet decayed due to the area's dry climate.
The barren landscape, once flooded with water from the nearby Tsauchab River, is now a hot spot for photographers — many of whom have captured the contrast between the claypan's bleached white floor and sun-scorched trees.
Pictures like the one above are typically taken from a very low angle, so that the sand dunes in the distance, tinted orange by the sun, look like a painted backdrop.
This "underwater waterfall" is not what it seems.
Along the shoreline of Mauritius, there appears to be a flowing river underneath the turquoise water of the Indian Ocean. While underwater waterfalls do exist, this isn't one of them. In this case, what looks like water is actually sand getting pushed off an underwater shelf called the Mascarene Plateau.
This salt flat in Bolivia is perfect for creating optical illusions.
Bolivia's Salar de Uyuni, the world's largest salt flat, transforms into a giant reflective surface when it's covered in a thin layer of water, either from rain or nearby overflowing lakes. Stretching on for miles, completely level, the salt flat also appears to have an endless horizon, allowing photographers to create illusions by playing around with depth and perspective.
Yosemite's Horsetail Fall looks like it's on fire at a certain time of the year.
Every year, around the second week of February, the setting sun hits Horsetail Fall in Yosemite National Park at a particular angle, illuminating the top of the waterfall. If the fall is flowing and the weather conditions are just right, the illuminated water glows bright orange and red, as if it's on fire.
The undulating patterns in this rock formation throw off your depth perception.
This unique rock formation is known as The Wave. It's located in Arizona, in the Coyote Buttes North area in the Paria Canyon-Vermilion Cliffs Wilderness. To see this stunning sight in person, however, you'll need to enter a lottery system to get a permit four months in advance.
This giant shadowy figure is a naturally occurring optical phenomenon.
Known as a Brocken Spectre, this phenomena occurs when an observer's shadow is cast onto the surface of clouds or thick mist. The head of the magnified figure is often surrounded by rainbow-colored rings — another optical phenomenon known as a glory, which is created when sunlight hits tiny water droplets suspended in the atmosphere and is scattered back toward the viewer.
At sea, objects in the distance may appear to be floating above the horizon.
A Fata Morgana is a complex, rapidly changing form of a superior mirage, an optical phenomenon that is created when light bends as it passes through a layer of air that is warmer than the layer below it.
Made up of several inverted and upright images stacked on top of each other, Fata Morganas appear as warped, often unrecognizable, objects or shapes that seem to float above the horizon.
It's easy to mistake simple mirages for bodies of water in the desert.
Compared to Fata Morganas, inferior mirages are created when air near the ocean or earth's surface is much warmer than the air above it. Light passing through these layers of air bends, producing an inverted, displaced mirage of an object (for example, a distant mountain range or the blue sky) that appears below the object itself.
On hot days, roads sometimes appear like they're wet.
This phenomenon is another example of an inferior mirage. Like sand in the desert, roads hold onto heat and warm up the air directly above it. Your brain then mistakenly perceives an inferior mirage of the sky as water on the ground reflecting light.
This isn't a lens flare from a camera.
Sundogs, or parahelia, are created when sunlight is refracted by ice crystals drifting in the air. The result is one or more patches of bright light located around the sun.
These are clouds, not UFOs.
Known for their saucer-like appearance, lenticular clouds are stationary clouds that usually form on the downwind side of a mountain range, given that the temperature is low enough. Under the right conditions, moisture in the air condenses to form these massive, striking shapes in the sky.
This moth has wings that look exactly like a snake's head.
When threatened, the atlas moth drops to the ground and flaps its wings. The tips of the insect's wings look incredibly similar to a snake's head, which allows the moth to scare off predators.
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