The Medusa (Fig. 1) is the only one of Caravaggio’s works to which the writer Giovan Battista Marino dedicated an ekphrastic poem. It is thought that Marino saw the work on a 1601 trip to Florence; by that time, the painting had been received in the armoury of the Grand Duke of Tuscany, Ferdinando de’ Medici. Collecting a painting in an armoury makes sense, of course, when the painting counts as arms––Caravaggio painted his Medusa on a convex shield, and Marino’s madrigal engages with just this aspect, addressing the Grand Duke:

Now what enemies will there be who will not become cold marble in gazing upon, my Lord, in your shield, that Gorgon proud and cruel, in whose hair horribly voluminous vipers make foul and terrifying adornment? But yet! You will have little need for the formidable monster among your arms: for the true Medusa is your valor.