You can see the little door behind the Papal throne? It leads into a lovely little room which leads to a staircase which led me into three choir galleries high above.
My pastor, the famous Church musician, Msgr. R.J. Schuler, once told me that when he was studying in Rome in the 1950s a porter of the Lateran once took him up there to show him where Jews were hidden during World War II. I saw many rooms up there where I guess they must have been hidden and where perhaps the canons or sisters live today.