Circumzenithal Arc

The circumzenithal arc or circumzenith arc (CZA), also called the Bravais' arc, is an optical phenomenon similar in appearance to a rainbow; but it arises from refraction of sunlight through horizontally-oriented ice crystals, generally in cirrus clouds, rather than from raindrops. It forms no more than one-quarter of a circle centered on the zenith and on the same side as the sun. Its colors are from blue on the inside to red on the outside of the arc.

23 June 2013, Vravrona, Attiki

Canon EOS 450d