Can you believe your eyes? When it comes to these head-twisters, chances are you cannot. From “God's burning finger” to the polar lights, here are 10 of the most extraordinary natural mirages that will leave you asking “Did you just see what I just saw?”.

Fata Morgana, Antarctica
Way up north (or way down south) the clear, pure air brings distant objects into sharp focus. Depth perception becomes impossible and the world takes on a strangely two-dimensional look. Fata Morganas are caused by light reflections off water, ice and snow. When combined with temperature inversions, they create the illusion of solid, well-defined features where there are none. Early explorers meticulously mapped islands, headlands and mountain ranges that were never seen again. One Swedish explorer described a craggy headland with two unusual symmetrical valley glaciers – when he was actually looking at a walrus!

St Elmo's Fire, Edinburgh, Scotland
Herman Melville called it “God's burning finger”. Caesar saw it on the javelins of his troops the night before battle. This spectacular effect (cause by the discharge of electricity from storm clouds to the earth) has always conjured thoughts of omens and divine intervention. Its name comes from St Elmo, a protector of sailors. Men at sea would welcome the sight, often seen on the mast of a ship during a storm, as it usually comes at the point where a storm is quietening down. The effect is also frequently seen on the heights of Edinburgh's Castle Rock.

Northern Lights, Alta, Norway
The Northern Lights are a dazzling Arctic and Antarctic display, with colourful sheets of light transforming the endless winter nights into natural lava lamps. Also known as the aurora borealis and aurora australis, the Northern Lights form when solar particles, thrown out by explosions on the sun, are drawn by the earth's magnetic field towards the north and south poles, colliding with atmospheric gases to emit photons, or light particles. What results are brilliant sheets of green, red, white, purple or blue light. At a latitude of 69 degrees north, the Norwegian town of Alta is renowned as an excellent base to see the lights.

Brocken Spectre, Goslar, Germany
For thousands of years, anyone lucky enough to witness this extraordinary optical phenomenon probably thought they were in the presence of God or undergoing their own spiritual rebirth. The traveller is confronted with an image of his or her shadow, surrounded by a halo of light, usually around the head. The phenomenon mostly occurs near mountain peaks when the air is moist and the sun is low. The name owes its provenance to the Brocken, which at 1,141m is the highest peak in the Harz Mountains that straddle the German province of Saxony-Anhalt.

Green Flash, St-Jean de Luz, France
A favourite of those with romantic imaginations, the Green Flash (or Green Ray) seems to capture something of the ineffable and transitory nature of existence. It is an effect seen at the end of the sunset, when a green spot or a green ray seems to shoot out of the sun. The causes of the illusion are complex and have to do with the refraction of light, the thickness of the atmosphere and the curvature of the earth. Try for a glimpse of it in St-Jean de Luz, the French town featured in Éric Rohmer's moody film Le Rayon Vert.

New-growth conifers, Mount St Helens, United States
This is one for a spring day. As you approach Mount St Helens in Washington state, you will see that the new, pale-green growth sprouting on the dark-green conifers forms an eye-bending pattern, almost like an op-art painting. Spread across the scale of the forest, the effect is startling. Mount St Helens erupted spectacularly in 1980, causing its north face to collapse in a shower of rocks and releasing a massive ash cloud. Fifty-seven people were killed and the landscape was instantly turned into a featureless moonscape. Since then, the area has been protected and allowed to re-generate. Visit the Mount St Helens National Volcanic Monument website to check out the webcam and visitor details.

Magnetic hill, Ladakh, India
A land of high snowy passes and ancient gompas on the borderlands of Tibet, Ladakh is the kind of place where your imagination can run away with you. Here you can encounter the phenomenon of a magnetic hill, also known as a gravity hill, where vehicles left out of gear appear to roll uphill. This astounding effect has led to stories about how the magnetic force pulls planes off course. But in fact this is just a powerful illusion -- the slope is actually slightly downhill, but the shape of the surrounding landscape and mountainous horizon obscure our usual reference points. The hill can be found 30km from the historic capital of Leh along the Leh-Kargil-Baltic highway.

Desert mirage, Nullarbor, Australia
This is a commonly observed phenomenon – a heat haze that makes the air shimmer and can make roads look wet. For exhausted travellers in brutal heat, the appearance of an illusory lake in the distance cruelly raises and then dashes hopes. On the other hand, if you are cruising comfortably along in a car with a bottle of mineral water at hand, the hazy refractions of light just add to the atmosphere of your road trip. Australia's Nullarbor Desert (its name means “no trees”) is the ultimate flat horizon. Driving along this seemingly endless road affords great opportunities for flirting with mirages.

Paasselkä devils, Lake Paasselkä, Finland
In England they are called will-o'-the-wisps or jack-o'-lanterns. In America they are called spook lights. The Scots call them spunkies. The phenomenon they are referring to is a light that appears at night, often in marshy ground. If followed it will back off; it can also appear to follow you. Most cultures have seen such lights as evil spirits, luring travellers to doom, or as harbingers of disaster. Finland's deep Lake Paasselkä is famous for mysterious balls of light. In Finnish folklore, the lights are believed to mark the sites of treasure.

Sun dogs, Timbuktu, Mali
A sun dog, or parhelion, is an effect seen around the sun. It looks like bright spots of light (or “mock suns”) sitting on either side of the sun itself and it can last for hours. In earlier times it was seen as a frightening omen of bad times ahead. But when you know it is just innocent ice crystals making prisms in the air, it is a lot less threatening. You will have the best chance of seeing one when the horizon is flat. Timbuktu's baked-sand vistas and ancient mud temples could make a good setting for a sighting.

The article 'The world’s strangest optical illusions' was published in partnership with Lonely Planet.