Detail of a gorgeous mosaic from the apse of the Leonine Triclinium, i.e., the papal dining hall, at the Lateran. This is all that remains of the extensive palace that once stood here, and these mosaics are believed to date to the late 8th-century AD. The square halos around the figures kneeling by St Peter (Leo III, and Charlemagne) indicate that they were still living when the mosaic was installed.
It shows St Peter bestowing a pallium, a symbol of authority, on Pope Leo III, and also bestowing a banner, a symbol of protection and power on Charles the Great, the first Holy Roman Emperor.
This is a fitting image for today, 10 November, the feast of Pope St Leo the Great, not just because of the pope depicted who also bears the name Leo, but because it shows the extent of papal authority deriving from St Peter, something that Pope Leo the Great was at pains to teach and show.