The Hall of the Colossus

The Colossus stood on a high podium made from blocks of tufa stone. It was part of the original design of the Hall and sculpted whilst the Hall itself was being built. The footprints still visible on the top of the podium, cut into the slabs of Pavonazzetto marble used to face it, show that the weight of the figure was resting on the left foot, (approx 177cm long) which was positioned in front of the right, (which was 166cm long) which was almost touching the wall behind.

L'aula del Colosso

Only three pieces still remain of this acrolithic statue (one in which the torso is made of wood or iron, usually concealed by drapery or gilding, and only the marble feet, head and hands are exposed), all of which are of white Greek marble from the Island of Paros. These three pieces are: the right hand which is clasping a symbolic circular object, the extended back of the left hand and a small part of the underside of the right forearm, perhaps just beyond the wrist. All have been modelled so that they can be attached to the supporting structure that was probably in wood. All are extraordinarily life-like thanks to the mastery with which the veins were carved with great delicacy and reality. 
A credible estimation of the height of the statue is that it was approximately 11 meters tall, a measurement that is borne out by markings on the wall behind it, and it was more than likely a representation of Genius Augusti (implying he was the son of Gods and father of men).
The wall at the back of hall, just behind the Colossus, was faced with rectangular slabs of white Luna marble (up to the height of the statue at least) that were slightly rounded to resemble draped fabric, a sort of backdrop, which was painted with decorative plant motifs. 

Foro di Augusto, Sala del Colosso