The architecture of Dante's Purgatory in the fifteenth century: the Hypnerotomachia Poliphili by F. Colonna and the Treaty of Architecture by A. Averlino

Dante's genius imagined Purgatory as a stepped mountain rising to the sky, set on an island surrounded by a deserted ocean in the southern hemisphere. Until then Purgatory was imagined as an antechamber of Hell. The poet's merit lies in having succeeded in uniting Purgatory with another fundamental "place of passage" in Christian culture: the Earthly Paradise. He places it at the top of Purgatory, as the final stage of a path of redemption that includes the ascent of Purgatory to the top, to enjoy the delights of the garden. It is precisely the theme of the fantastic island that creates a profound link between Dante's work and the humanistic panorama. The Hypnerotomachia Poliphili by Francesco Colonna is an encyclopaedia of knowledge that is the full expression of the humanistic culture of the 15th century. It can be considered the humanistic transposition of Dante's journey, with the same point of departure (the forest) and the same point of arrival. The amphitheatre on the island of Kythera appears as a Paradise garden, a descendant of the idea of Paradise that Dante had well expressed in the Comedy. Antonio Averlino wrote the Treaty of Architecture between 1460 and 1464, dedicating it to the Duke of Milan Francesco I Sforza. Reading the work, we can see the same affinity between the utopian architectures of Filarete and the Hypnerotomachia. The garden-palace imagined on the periphery of Sforzinda recalls the idea of the green mountain and is perfectly inserted within the symbolism of the sacred mountain that ascends to heaven, crowned by the earthly paradise, born with Dante. Placed inside a structure that includes the Labyrinth and the Island, it is a descendant of that "point of arrival" that in Dante's Christian conception was the earthly paradise, transformed into the Amphitheatre of Venus with Colonna's neoplatonic vision.