They sometimes look like big donuts or ice tires, as if nature itself came to play snowball with us. It is a rare meteorological phenomenon that is generally cylindrical in shape.

The reason why they are hollow in the middle is that those are the first layers to get formed, and thus they are weak and fragile and easily get blown away by the wind, making it look like a donut. These can be as small as a tennis ball and as big as a car.