Perhaps the most prominent arc of the natural world
appears in the elusive form of the rainbow, which primitive man saw as a
bridge between the Heavens and the Earth.
As a part of a circle, the arc symbolizes potential
spirit. The position of the arc is important. Upright, shaped like a cup
or chalice, it implies the feminine principle, something that can
contain the spirit. If the arc is inverted, then the opposite is true
and it becomes a triumphal, victorious, masculine symbol. As such, the
arc can take the form of an archway. The vaulted or arched shape of many
holy buildings, from a great variety of different faiths, represents
the vault of the Heavens. The arc shape often appears in planetary
symbols.