THE QUINCUNX AS ARCHITECTURAL STRUCTURE. GEOMETRY AND DIGITAL RECONSTRUCTIONS AFTER LEONARDO DA VINCI’S CENTRIC PLAN TEMPLES

The quinconce is a five once bronze coin with five points on one of its faces as disposed as on a modern die: four in the corners and one in the middle. In architecture, the Latin term quincunx is instead used to label a building with four pillars (tetrastylum) dividing a square plan in nine parts, and five domes as disposed as the points on the coin. Originally this term mainly described buildings first of the Armenian and then Byzantine and Arab tradition (Krautheimer), but related designs feature martyrium and tetrastylum atrium in Roman religious and thermal buildings (Chiolini). From 6th to 9th century, this plan was adopted for Christian churches and the term was further enriched with iconographic connotations of the Holy Land and the Celestial Jerusalem (Cardamone). At this point, it was already involving some formal variations. The plan could be square or rectangular; include a cross of cells covered with vaulted ceilings; do without the five domes and instead have one or three apses and also an external narthex. In practice, quincunx came to embody the idea of centric building featuring different buildings which share a square centric plan divided into nine zones and is also used a modular unit for larger churches such as Saint Front in Perigueux (Purves). While in the Venetian territory the antiquarian reference to the “middle body of the church of S. Marco” persisted, 15th and 16th century geometrical and typological explorations on quincunx grounded the renaissance studies on centric temple climaxed by Bramante’s application of quincunx to St. Peter’s church plan (Bruschi). A central role in bridging this Middle-Age heritage to Renaissance forms is played not only by architects such as Francesco di Giorgio (Fiore), Filarete and Tramello (Adorni) but also by Leonardo da Vinci (Pedretti). From 1482 to 1499, he was at the Sforza’s court in Milan and produced an amount of architecture drawings. He dedicated at least six sheets to quincunx studies (Cod. Atl.; Ms.B; Cod. Ash.), here enquired by authors through critical approach to his sketches, digital re-drawing, re-designing, and three-dimensional modeling after some of them. The analysis of them can demonstrate not only evidences of his direct engagement in the restoration of S. Maria presso San Satiro (Schofield), a little quincunx church, but also a series of explorations on geometric and compositional opportunities of the tetra-lobed tetrastyle quincunx as either an autonomous structure or combined with radial structures (Di Teodoro). The sheets reveal also the shift from the contingent questions of a specific building to a wider speculation on geometric and architectural properties of a grid centric structure, which is not only the effect of Leonardo’s attitude to generalize but also a key to an innovative mathematical approach to architectural composition that made its way up to the 20th century “nine-square grid problem”.