The Available Space

Sometimes the lowest octave of a rank of pipes in the organ, which is normally fixed in a vertical position on the windchest, is mounted horizontally, the pipes stacked one upon another, to make the most use of the available space.
Photo shows the 32 foot Contra Gamba (metal) and 32 foot Contra Diaphone (wood) of the String Pedal division of the Wanamaker Grand Court organ, Philadelphia, PA, the largest fully functional pipe organ in the world.