"What makes this church so architecturally fascinating is the fact that the present building is formed from the union of two plainly visible structures. As one proceeds down the nave and up the steps to the altar (all belonging to the thirteenth-century building), the capitals and upper shafts of the columns of the original sixth-century church come into view on either side. Leaning over the railing of the chancel, you can see the rest of these columns with their bases and pedestals twelve feet below." (Robert Kahn (Ed.): City Secrets Rome: The Essential Insider’s Guide, 2011).