Lunette
A lunette is an arching aperture in a wall or concave ceiling, It may be crescent-shaped or semicircular. The word is the French diminutive of lune, "moon." Lunettes may function as windows, they may form a cove for ornament or statuary, or they may be simply a section of wall framed by an arch or vault. In the last case, the area will sometimes be decorated with a mural.