Final answer:
In the civil basilica, the altar replacing the emperor's statue would be located at the rear of the building, typically installed in the apse situated at the end of the central nave.
Step-by-step explanation:
The location where the emperor's statue was placed in the civil basilica corresponds to the part of the structure that was designed to emphasize the importance and authority of the emperor. Given the way that civil basilicas were constructed to be imposing stages for the emperor during their dramatic adventus or entrance, and considering the architectural design elements of basilicas at the time, with a focus on the apse as the locus of power, we can infer that the altar, replacing the emperor's statue, would be at the rear of the basilica. This conclusion is supported by historical insights into basilica structures like the Aula Palatina in Trier and the configuration of spaces in buildings such as the basilica of San Vitale in Ravenna, Italy. In the traditional layout of a basilica, the altar is typically installed in the apse situated at the end of the central nave, which is at the rear of the building.