On the inside, the church looks much like other Italian churches of that time, but if you look closer, you see not only three naves as in a usual basilica, but five of them - two of each original church and one big and new in the center.
The church is asymmetric (look at the columns on both sides), because the two joined churches were different in architecture. If you’re there, look into those details. It’s extremely interesting and pleasing.