Circumhorizontal arc over Ohio, May 2009.
For a circumhorizontal arc to be visible, the Sun must be at least 58 degrees high in a sky where cirrus clouds are present. Furthermore, the numerous, flat, hexagonal ice-crystals that compose the cirrus cloud must be aligned horizontally to properly refract sunlight in a collectively similar manner.
Credit & Copyright: Todd Sladoje
Mirror to The Milky Way by Dakotalapse
Mirror - A few inches of water cover the salt flat of Salar de Uyuni in Bolivia. When it is calm it creates an excellent mirror for the sky. This was after 3AM and the Milky Way core was directly over head, so it is out of the frame.