"Quantunque l'una d'este chiavi falla,
che non si volga dritta per la toppa,"
diss'elli a noi, "non s'apre questa calla …
"Whenever faileth either of these keys
So that it turn not rightly in the lock,"
He said to us, "this entrance doth not open …
—Dante Alighieri, Purgatorio: Canto IX, lines 121–123
Inspired by the humour and attention to detail in Dante’s Divine Comedy, the sculpture is a metaphor for the gateway to purgatory. The spirit of the porter-angel is represented by a bodiless spiral with three hollow-eyed faces in a ghost-like head; the open mouth is speaking. The spiral movement symbolises the workings of the intricate lock on the gates. The porter holds the two keys and the hinged wings represent the opening and closing of the gate.