Venice was a center for numerous bronze founders who made elaborate doorknockers for palace doors throughout the city. Although utilitarian, these objects were meant to impress as works of art in their own right. The presence of snakes which coil out from the fearsome head suggest that this being is Medusa, one of the three demon sisters in Greek mythology known as the Gorgons.
According to some legends, Medusa was an attractive woman who, after having an affair with the god Poseidon in Athena's temple, was transformed by the goddess into a serpent-haired beast. Her visage was so terrifying that anyone who looked at it was turned to stone. The hero Perseus was ordered to decapitate Medusa, and Athena subsequently placed the monstrous head in the center of her shield or breastplate. The use of the Gorgon's head as an ancient motif and protective symbol to avert evil developed from this fabled act. Such literary and iconographic traditions were known to Renaissance artists, and the presence of a Gorgon head on a doorknocker almost certainly evokes its guarding function for a Venetian home.
--Lauren Maceross (May 2013)