Final answer:
The Arch of Constantine's distinguishing feature is its use of spolia, reusing elements from the reigns of previous emperors to symbolize continuity and legitimacy. It showcases both a shift in artistic style from classicism to Late Antique and conveys a political and religious message of universal appeal.
Step-by-step explanation:
The distinguishing feature of the Arch of Constantine is its extensive use of spolia, which are architectural and decorative elements taken from other monuments to be reused. Interestingly, the arch incorporates pieces from prior emperors such as Trajan, Hadrian, and Marcus Aurelius, who were all considered to be good emperors during the Pax Romana.
The use of spolia not only reclaims the glory of past rulers by recycling physical aspects of their governance but also confers legitimacy and continuity to Constantine's own emperorship.
The artistic style depicted through the frieze on the arch captures Constantine's rise to power, contrasting the classical style with that of the Late Antique period. A key component is a schematic representation where figures are depicted with rigid, stiff garments which is noticeable in scenes like Constantine distributing gifts atop a throne.
This iconography was different from the classical Roman artistic norms that usually displayed the intricate and careful detailing of figures.
Furthermore, the arch symbolizes a symbolic and political message that links Constantine to the legacy of Rome's revered leaders while subtly integrating Christian undertones. This is exemplified through an ambiguous inscription attributing Constantine's victory to 'divine inspiration', appeasing both Christian and traditional polytheist populations.