Here is a picture of the Christian basilica in Ostia antica from about the 4th Century. Perhaps this is one attended by Augustine. If you have eyes to see, Kris is at the back.
The path is right through the center of the basilica; the pillars separated each nave. Two things struck me about this basilica:
First, that the name “basilica” is also the name the Romans used for their central legal building.
Second, that this Christian basilica was in the heart of the city of Ostia antica, surrounded by pagan shrines and homes and legal buildings.