Chapel of St. Sebastian, Basilica of St. Peter in Chains, Rome
The letters flanking the figure spell out SANCTUS SEBASTIANUS. This must be how St. Sebastian was imagined before the convention of showing him stripped and tied to a tree stump: dressed as a courtier proffering a crown, like the martyrs processing to Christ's throne in Ravenna and elsewhere.
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Photographed at the basilica by Richard Stracke, shared under Attribution-NonCommercial-ShareAlike license.