In Antarctica, particularly in the region around the South Pole, there is an amazing optical phenomenon that occurs - an unnaturally curved horizon as the sun moves parallel to the ground.

What causes this?

The extreme angle of the sun - During the Antarctic summer, the sun never sets, but instead moves in a circular path, barely rising above the horizon. This causes its light to slide across the landscape, creating strong optical distortions.
Atmospheric refraction - The cold air and different layers of air cause light to bend, making the horizon appear concave or elevated.
Lack of visual landmarks - In a white desert with no trees or buildings, the brain has no familiar reference points to help it interpret the scene, further enhancing the illusion of a curved horizon.