With improved realism in computer graphics, 3D animation has been applied in many different field, from architectural visualization to feature film works. The advantage of CGI work is the ability to reproduce environments that are inaccessible, imaginery, or disappeared.
Feature film set in historical times nowadays uses CGI work as backdrop. Ancient Rome can be reconstructed much more easily and afforadbly using CGI work than building an actual mock up. As technology improves even more, we predict this will become more and more common in the future, where CGI work begins and live footage stops will become indistinguishable.
Here is a short demo of 3D historical and archaeological works based on ancient China.