Chromostereopsis is a visual illusion in which the impression of depth is conveyed in two-dimensional color images. This 1564 stained-glass window, in the Bielsko-Biała Museum and Castle in Poland, exhibits this effect, with contrasting depth perception in the red and blue areas. The window, an example of Standesscheibe, depicts the coat of arms of Unterwalden, a canton of the Old Swiss Confederacy.Stained-glass credit: unknown; photographed by Jan Mehlich