Ice pillars over Finland Finland (Photo: Timo Newton-Syms/Flickr)

Thin, colorful ice pillars appear in the night sky above Ruka, Finland.

This stunning visual phenomenon occurs when light reflects off horizontally faced ice crystals hovering in the air. The pillars, which are often mistaken for UFO sightings, are produced by sunlight, moonlight or artificial man-made light situated along the horizon.

Like auroras, this beautiful light display is only visible in the coldest regions of the planet.

Ice pillars over Granby, Colorado Granby, Colorado (Photo: Eric Magnuson/Flickr)

Ice pillars over Moscow, IdahoMoscow, Idaho (Photo: Jasper Nance/Flickr)

Ice pillars over Laramie, WyomingLaramie, Wyoming (Photo: Christoph Geisler/Wikimedia)

Ice pillars over Anchorage, AlaskaAnchorage, Alaska (Photo: Nat Wilson/Flickr)