In 1550 Vasari wrote about Leonardo: «And among all these models and drawings there was one which he showed several times to the many intelligent citizens then ruling Florence, to demonstrate how he wanted to raise the church of San Giovanni and place steps under it without destroying it; and he persuaded with such good reasoning that they thought it possible, even though, upon leaving him, each of them realised the impossibility of such an undertaking.»

In reality, Leonardo's project already had precedents. A few years earlier, in 1455, the Bolognese engineer and architect Aristotile Fioravanti (c. 1415-1486) had successfully moved a tower in Bologna, with the aid of rollers, beams and jacks. Fiorovanti had also worked for some of Leonardo's friends and clients, such as the Bentivoglio family, King Mattia Corvino of Hungary and Cosimo de’ Medici (between 1458 and 1467 in Florence).

Leonardo's project called for raising the Baptistery on four steps, as can be seen in a drawing attributed to Francesco Granacci (now in the Uffizi Cabinet of Drawings and Prints) and in two replicas of the Baptistery ("Ancient temple of Mars, today of St. John") published in the Discorsi [Discourses] of Vincenzo Borghini (Florence, Giunti, 1584). The model was rebui

lt in 2007 and is displayed today at the Museo del Bigallo in the "Leonardo in Florence" section.

The Cathedral of Florence, and Brunelleschi's Dome in particular, were fundamental to Leonard's formation especially as regards knowledge of the principles of church architecture and the operation of construction site machines.

This interest clearly emerges in the numerous drawings of churches with central plan and of winches and cranes, in the memorandum on the gilded bronze sphere and the screws of Santa Reparata, and in the sketches of herringbone vaulted roofs and various structural and decorative elements.

In 1515 Pope Leo X (Giovanni di Lorenzo di Piero de’ Medici, 1475-1521), while travelling to Bologna to meet the new King of France, Francis I (future patron of Leonardo), stopped in Florence, at Santa Maria Novella and then at the Medici Palace in Via Larga. On November 30th the city held extraordinary festivities in his honour. Old and new acquaintances of Leonard's such as Baccio d’Agnolo, Piero di Cosimo, Pontormo, Andrea del Sarto, Francesco Granacci, Jacopo Sansovino and Antonio da Sangallo il Vecchio, also collaborated on the scenography and organisation of the event.

At this time there arose the idea of rearranging the section of Florence between Piazza San Marco and Piazza San Lorenzo and completing the facade of the San Lorenzo church.

Leonardo worked on a project consisting of several parts, including the following initiatives: constructing a Medici Palace, opposite that of Cosimo the Elder (today's Palazzo Medici Riccardi); demolishing the Church of San Giovannino (built in 1351 and still existing today, with the facade rebuilt around 1843, in Via Martelli on the corner with Via Gori) and rebuilding it in front of the new Medici Palace; providing a facade for San Lorenzo and enlarging the square in front of it; a new arrangement of the San Marco area, including the Medici Stables, which Leonardo called, in the Codex Atlanticus, "Stables of the Magnificent", because they had been built for Lorenzo di Piero de’ Medici (nephew of the pope, elected Governor of Florence in that same 1515). Between 1515 and 1516, a building between San Marco and Santissima Annunziata that matched Leonardo's sketch was in effect constructed. And in the mid-sixteenth century the Lion Menagerie was moved to the former Via del Maglio (since 1877 Via Lamarmora, in the section recently renamed for Giorgio La Pira). In 1592 Ferdinand I de’ Medici had the present-day stables built. Still today the architectural complex, which includes the Rectorate of the University, the Istituto Geografico Militare and the Santissima Annunziata Convent, constitutes an exceptionally interesting area for seeking out and visiting the places linked to Leonardo.

Other architects too worked on these projects, such as Antonio da Sangallo, Baccio d’Agnolo, and above all Michelangelo, who was commissioned to design the facade of San Lorenzo, never realised (the wooden model is now in the Casa Buonarroti museum in Via Ghibellina).

In the place where Leonardo, around 1515, had planned to build the new Medici Palace, the present-day Palazzo Panciatichi (seat of the Regional Council of Tuscany) and Palazzo Capponi-Covoni were built and subsequently remodelled.

The latter is especially interesting for the intricate relationships between its various owners, Leonardo himself and historic Florentine families such as the Tani and then the Portinari, directors of the Medici Bank in Bruges, through whom Leonardo asked information on ice-skating in Flanders; and still others, such as Andrea di Paolo Carnesecchi, Consul of the Florentine Republic at Constantinople at the time when Leonardo was designing the bridge for the sultan of that city, and indirectly the Capponi family, descendants of that Neri di Gino Capponi who, «being General Commissioner of the Florentines defeated the armies of the Duke of Milan at the Battle of Anghiari» (portrayed by Leonardo in the "sumptuous cartoon" drawn in Santa Maria Novella and recorded in the 18th century in Palazzo Medici Riccardi). These traces are even more evocative considering that the seat of the Regional Council and the "Chanto di Via Largha" are only a few metres away from the house of Piero di Braccio Martelli (today the seat of the Liceo named for Galileo, adjacent to the Ximenian Observatory, an institute specialized in meteorology and geophysics), in which Leonardo spent many years of his second Florentine period.

Returning to Florence in the year 1500, Leonardo was consulted in regard to the new bell tower of San Miniato, designed by Baccio d’Agnolo, and the static problems of the church of San Salvatore a Monte below it (the church called by Michelangelo «la bella villanella»).

In the Strozzi Papers in the Florence State Archive we can read the opinion of Leonardo, recorded after those of Jacopo del Pollaiolo, known as Cronaca, and Giuliano da Sangallo: «Lionardo da Vinci said what was wrong with San Salvadore. He has remedies for it, as he has shown in a drawing, in which can be seen the problems of the building and the water that penetrates among the layers of stones down to the bricks, and here in part the layers are cut, and that part of the building where the layers are cut, and are lacking, and he showed that the layers could be remade and cut and put back in place. And how to keep the sewers clean».

In the Codex Arundel, Leonardo had been concerned with the breakage of the walls and their repair. In regard to the lantern on the Milan Cathedral, he had already noted in the Codex Atlanticus the similarity between the physician and the architect in terms of "harmony of the elements". Leonardo considered buildings, in fact, to be living organisms having need, when "ill", of an "architect/physician". «Just as physicians, tutors, curers of the ill, must know what man is, what life is, what health is, and how the equality, the harmony of elements maintains them, and how discordance among them ruins and destroys them; and having a good knowledge of the aforesaid natures, can better provide a remedy than one who lacks such knowledge […]».

"Fatevi dare la difinitione e riparo del caso al Santo e all’altro e vedrete che omini son eletti per medici di malatie da lor non conosciute" (f. 147v, P82).

Along Via Santa Margherita a Montici, which leads from the church to Piazza Calda and then runs downhill to the Villa di Rusciano, we find what was the Villa La Torre, later "La Bugia", which belonged to the Guicciardini family from 1507 to 1634, then to the Nerli and lastly to the Morrocchi. It had been built in the past by the Amidei and on September 4, 1470 it was sold by Giovanni Francesco Amidei to Agnolo di Lapo del Tovaglia, who had it enlarged and remodelled by the Medicean architect Lorenzo da Montaguto between 1480 and 1490.

On August 11, 1500 Francesco Malatesta sent from Florence to Francesco II Gonzaga, at the latter's request, a drawing of the villa done by Leonardo, as well the project for replicating it. Malatesta specifies: «I am sending Your Illustrious Lordship the drawing of Agnolo Tovaglia's house done by the hand of Leonardo Vinci… The aforesaid Leonardo says that to make a perfect thing, it would be necessary to transport this site which is here, there where Your Lordship intends to build [...] I have not had the drawing coloured, nor had the ornaments of verdure, of ivy, of boxwood, of cypresses, nor of laurel added, as they are here, since I thought there was little need of them: but if Your Lordship wishes, the aforesaid Leonardo offers to do so in both the picture and the model».

In effect, the architecture of this building complex (with the core of the medieval tower, the villa with its hortus conclusus, greenhouses and lemon houses), in spite of the discontinuity due to remodelling and additions, is remarkable, especially in relation to the magnificent landscape of the Florentine hills, rising like an airy balcony over the valley of the Ema.

It is interesting to note that Bartolomeo del Tovaglia was one of the bankers recorded by Leonardo in a memorandum in the Codex Atlanticus dating from the late 15th century as one of his correspondents from France and Flanders.