The Basilica, on the northern boundary of the Forum, was begun in 307 by Co-Emperor Maxentius.
Constantine completed the Basilica after he defeated Maxentius at the Battle of the Milvian Bridge in 312.
Constantine seems to have reorientated the building, changing the site of the principal entrance and adding a new northern apse.
With these changes, including the great statue in the west apse, Constantine publicly and visibly declared his overthrow of his vanquished adversary.
Precise dating of the statue itself is problematical; it has been suggested that a date of 312–315 for the initial creation of the statue is likely from political considerations, whilst a substantial reworking of the features some time after 325 is indicated on art-historical grounds.

The Colossus was pillaged sometime in Late Antiquity, most likely for the bronze body portions.
The marble portions of the statue were brought to light in 1486.
The surviving remnants were later removed from the Basilica and placed in the nearby Palazzo dei Conservatori Courtyard by Michelangelo, who was working in the area.
Strangely, there are two right hands (with upraised index fingers) amongst the remains of the statue, which differ slightly.
It has been proposed that the statue was re-worked at some time late in Constantine's reign and a hand holding a sceptre was replaced by a hand holding a Christian symbol.

The marble fragments underwent restoration during 2000–2001.
Between 6 and 10 February 2006, a 3D laser scan of the fragments was carried out on behalf of the Land of Rhineland-Palatinate in collaboration with the Capitoline Museums in Rome.
 Both reconstruction and castings were displayed from 2 June to 4 November 2007 as part of the major cultural and historical “Constantine the Great” Exhibition in Trier, Germany.
The Basilica, on the northern boundary of the Forum, was begun in 307 by Co-Emperor Maxentius. Constantine completed the Basilica after he defeated Maxentius at the Battle of the Milvian Bridge in 312. Constantine seems to have reorientated the building, changing the site of the principal entrance and adding a new northern apse. With these changes, including the great statue in the west apse, Constantine publicly and visibly declared his overthrow of his vanquished adversary. Precise dating of the statue itself is problematical; it has been suggested that a date of 312–315 for the initial creation of the statue is likely from political considerations, whilst a substantial reworking of the features some time after 325 is indicated on art-historical grounds.
The Colossus was pillaged sometime in Late Antiquity, most likely for the bronze body portions. The marble portions of the statue were brought to light in 1486. The surviving remnants were later removed from the Basilica and placed in the nearby Palazzo dei Conservatori Courtyard by Michelangelo, who was working in the area. Strangely, there are two right hands (with upraised index fingers) amongst the remains of the statue, which differ slightly. It has been proposed that the statue was re-worked at some time late in Constantine's reign and a hand holding a sceptre was replaced by a hand holding a Christian symbol.
The marble fragments underwent restoration during 2000–2001. Between 6 and 10 February 2006, a 3D laser scan of the fragments was carried out on behalf of the Land of Rhineland-Palatinate in collaboration with the Capitoline Museums in Rome.  Both reconstruction and castings were displayed from 2 June to 4 November 2007 as part of the major cultural and historical “Constantine the Great” Exhibition in Trier, Germany.
Colossus of Constantine