The great head, arms and legs of the Colossus were carved from white marble, while the rest of the body consisted of a brick core and wooden framework, possibly covered with gilded bronze.
 Judging by the size of the remaining pieces, the seated, enthroned figure would have been about 12 meters (40 feet) high.
 The head is about 2½ meters high and each foot is over 2 meters long.

The statue's hand may have held a staff with the sacred monogram XP affixed to it.
Medals that Constantine minted around this time show him so decorated.
An inscription is said to have been engraved below the statue:
Through this sign of salvation, which is the true symbol of goodness, I rescued your city and freed it from the tyrant's yoke, and through my act of liberation I restored the Senate and People of Rome to their ancient renown and splendor.

The great head is carved in a typical, abstract, Constantinian style (“hieratic emperor style”) of late Roman portrait statues, whereas the other body parts are naturalistic, even down to callused toes and bulging forearm veins.
  The head was perhaps meant to convey the transcendence of the other-worldly nature of the Emperor over the human sphere, notable in its larger-than-life eyes which gaze toward eternity from a rigidly impersonal, frontal face.
 The treatment of the head shows a synthesis of individualistic portraiture: aquiline nose, deep jaw and prominent chin characteristic of all images of Constantine, with the trends of Late Roman portraiture which focus on symbolism and abstraction, rather than detail.

Constantine is enthroned in this great public work in unapproachable grandeur, like the effigy of a god, although he is really intended to reflect the Christian deity.
According to Michael Grant:
Here was the man at whose court...writers felt it appropriate to speak of the 'Divine Face' and 'Sacred Countenance'.
The sculptor has conceived this countenance as a holy mask, an overpowering cult object resembling, though on a far greater scale, the icons of future Byzantium: an idol animated with the divine presence, and with the power to repel the demons lurking in pagan images.
The great head, arms and legs of the Colossus were carved from white marble, while the rest of the body consisted of a brick core and wooden framework, possibly covered with gilded bronze.  Judging by the size of the remaining pieces, the seated, enthroned figure would have been about 12 meters (40 feet) high.  The head is about 2½ meters high and each foot is over 2 meters long. 
The statue's hand may have held a staff with the sacred monogram XP affixed to it. Medals that Constantine minted around this time show him so decorated. An inscription is said to have been engraved below the statue:
Through this sign of salvation, which is the true symbol of goodness, I rescued your city and freed it from the tyrant's yoke, and through my act of liberation I restored the Senate and People of Rome to their ancient renown and splendor.
The great head is carved in a typical, abstract, Constantinian style (“hieratic emperor style”) of late Roman portrait statues, whereas the other body parts are naturalistic, even down to callused toes and bulging forearm veins.   The head was perhaps meant to convey the transcendence of the other-worldly nature of the Emperor over the human sphere, notable in its larger-than-life eyes which gaze toward eternity from a rigidly impersonal, frontal face.  The treatment of the head shows a synthesis of individualistic portraiture: aquiline nose, deep jaw and prominent chin characteristic of all images of Constantine, with the trends of Late Roman portraiture which focus on symbolism and abstraction, rather than detail.
Constantine is enthroned in this great public work in unapproachable grandeur, like the effigy of a god, although he is really intended to reflect the Christian deity. According to Michael Grant:
Here was the man at whose court...writers felt it appropriate to speak of the 'Divine Face' and 'Sacred Countenance'. The sculptor has conceived this countenance as a holy mask, an overpowering cult object resembling, though on a far greater scale, the icons of future Byzantium: an idol animated with the divine presence, and with the power to repel the demons lurking in pagan images.
Colossus of Constantine