In the 13th century, St.Mark’s Basilica in Venice was considerably enlarged and refurbished; its external walls were encrusted with rare marbles and adorned with a collection of sculptures, in part expressly commissioned, in part spolia, some of which very ancient and illustrious.

Among them are the two ‘Formelle di Ercole’, a couple of rectangular bas-reliefs depicting some of the Herculean Labors, still located on the main facade. The one on the left represents Hercules with the Erymanthian Boar, and is reputed to be a late-antiquity (IV century AD) Roman original. Its pendant on the opposite side condenses two other Labors in one representation, showing Hercules with the Ceryneian Hind on his back and the Lerneian Hydra at his feet. Strongly resembling its companion in format and style, this second piece has long been considered of the same age, i.e., a late-Roman original; but more recent philology tends to see in it a rather shrewd imitation, created in Venice in the 13th century.

In this talk, we outline the possible and hitherto unnoticed astronomical content of the two bas-reliefs.

Although already veiled in the classical myth, the celestial tale behind Herakles and the Erymanthian Boar has come to us singularly well-preserved, to the point that if we replay it on a virtual planetarium such as Stellarium, we see several apparently bizarre and incoherent details regain their place and meaning within the narration.

Representing two other Herculean labors in an imitation piece, the 13th-century Venetians showed to the discerning eye that they were aware of the astronomical myth behind the Roman sculpture.  They did even more: they located the two formelle side to side on the facade in a distribution which, together with other pieces of different ages and provenience, resonates correctly with the astronomical orientation of the building.

Essential bibliography

Panofsky, Erwin,  Studies in iconology, New York, Oxford University Press, 1939

Centanni, Monica, Due tappe del viaggio di Ercole in Italia tra XIII e XV secolo: Venezia, Rimini, in: Le strade di Ercole. Itinerari umanistici e altri percorsi, seminario internazionale per i centenari di Coluccio Salutati e Lorenzo Valla (Bergamo 25-26 ottobre 2007), a cura di Luca Carlo Rossi, Firenze, Sismel. Edizioni del Galluzzo, 2010, pp. 189-210

Frugoni, Chiara,  Ercole, in Enciclopedia dell’arte medievale, Milano, Treccani, 1994, https://www.treccani.it/enciclopedia/ercole_(Enciclopedia-dell'-Arte-Medievale)/