The pavilion of a diamond is the part from the girdle in the middle to the culet at the bottem. This is actually the lower half of the diamond. If the pavilion is cut too deep or not deep enough, the diamond will let light escape and lose its shimmer and brilliance. This is based on the physical properties of the diamond that determine the angle at which light is best reflected and, consequently, how deep the pavilion may be sharpened. The cut of a diamond always determines his look and glimmer.