Brunelleschi: Linear perspective and the Hospital of the Innocents

When Filippo Brunelleschi (1377 – 15 April 1446) was 21 years old he became a master goldsmith, and by the age of 22 he was registered as an apprentice in the Arte della Seta (the silk merchants’ guild) of Florence, by then the wealthiest and most prestigious guild in the city, where he did some watchmaking work. Soon later he produced his first sculptural works in bronze along with Donatello, who declared himself defeated in a competition in which both participated in order to make an image of a crucified Christ. Brunelleschi abandoned everything to devote himself to architecture and to develop a new concept of space that aligned to the sensitivity of the time. He developed the mathematical technique of the principles of linear perspective, a genial invention to represent three-dimensional space on a flat surface. His incredible intellectual fertility to develop his ideas on perspective as a method for analyzing space, which he applied in his work as we will see later, is revealed in the fact that for almost 500 years (until the development of Cubism by Picasso) painters didn’t conceive of another way of representing three-dimensional space despite the fact that, since the third decade of the 19th century, the camera was able to perform the same operation though by mechanical means.

As G. C. Argan explained in his paper “The Architecture of Brunelleschi and the Origins of the Perspective Theory in the Fifteenth Century” (Journal of the Warburg and Courtauld Institutes, Vol. 9. 1946), in the perfect forms of his architecture, Brunelleschi expressed not only a new and grand conception of the world, but a new condition of the human mind. This is evidently apparent in all his work and, most of all, in the dome of Santa Maria del Fiore where the whole significance of the monument was not the expression of the old medieval society that built the temple, but represented the expression of the current mindset of the Florentine society of those times. To this end, Brunellescchi designed the double dome not only because of technical reasons required by force mechanics (which we discussed before), but for a specific formal reason: “to make it more magnificent and turgid” according to the words of Brunelleschi himself (“perché la torni piú magnifica e gonfiata”). That is, the purpose of the double dome, from his point of view, is to differentiate its proportions depending on whether they relate to the inner empty spaces or to the full volumes with the distribution of their masses of the exterior. In fact, seeing from the inside, the dome has no ribs or rays, and where the spherical triangles met determine curved dihedral angles; in this way, the internal dome coordinates the various spatial directions of both the nave and the octagonal drum, and leads them to the deep empty space towards the lantern in accordance with the laws of perspective. Instead, on the outside, where it is about coordinating masses and not empty spaces, the dome’s spherical triangles (more slender because here they are pointed) appear as tense pink membranes among the powerful framework of the white marble ribs that lead the mass movement of the building to the airy lantern that crowns the top of the dome.

The portico of the Ospedale degli Innocenti in Florence (Italy). The building, designed by Brunelleschi, was built between 1419-1445. Brunelleschi was the official architect until 1427, but the hospital was later completed by Francesco della Luna in 1445. In the spandrels of the arches there are glazed blue terracotta tondos with reliefs of babies designed by Andrea della Robbia which suggest the function of the building as it originally was a children’s orphanage. This building is a famous example of early Italian Renaissance architecture.

Brunelleschi, who had systematically studied ancient Roman architecture, did not propose (as many commentators have repeated) to imitate classical antiquity. His starting point was logically the architectural facts he had before his very eyes: the Romanesque and Gothic buildings of Tuscany. This is evident if we look at other buildings he designed and directed in Florence. In 1419 Brunelleschi was commissioned by the Arte della Seta guild to build a children’s orphanage. The silk guild was one of the wealthiest in Florence and, like most guilds, took upon itself philanthropic duties. This building was designed by Filippo and constructed in several phases, though he directly supervised only the first phase (from 1419-1427). During his supervision, he built the portico of this Ospedale degli Innocenti (Hospital of the Innocents), as this building was named. This is the first architectural work of the Renaissance and is regarded as a notable example of early Italian Renaissance architecture, its general design shows a clean and clear sense of proportion, and was precisely this desire for regularity and geometric order that was to become an important element during the height of Renaissance architecture. In the Hospital’s arcade, a series of columns with a smooth shaft and Corinthian-Composite capitals support a series of semicircular arches on top of which a classical cornice runs over, while a row of tabernacle windows (rectangular windows with a triangular pediment on the top) open on the wall. All the above-mentioned elements (columns, arches, cornices, pediments) have disoriented many commentators who, after observing this monument, have proclaimed a resurrection of the ancient forms. However, careful observation shows that neither Greece nor classical Rome ever produced anything like it. For example, the arches that rest on very thin columns are as different from those of the Flavian Amphitheater or Colosseo in Rome as they are from the Gothic arches of northern France. The Greeks never used the arch and the Romans always supported them on square pillars, except in late works such as the Diocletian’s Palace in Split, where by Syriac influence the arches rest on columns as they do in medieval architecture. On the other hand, in works of the Florentine Romanesque of the 11th and 12th centuries such as the church of San Miniato al Monte, these same semicircular arches appear resting on smooth columns and encased in classical moldings. In addition, the existence of abacuses on each of the capitals of this Brunelleschi’s portico also demonstrates that it was a return to the Tuscan Romanesque. In sum, the building’s design was based on Classical Roman, Tuscan (Italian) Romanesque and late Gothic architecture.

Another view of the arcade of the Hospital of the Innocents from Piazza della Santissima Annunziata with the fountain by Pietro Tacca from 1629.

When seen from inside, this portico of the Ospedale degli Innocenti shows the proportional logic typical of Brunelleschi, the arches are not only architectural elements that support the mass over the void, but have been used as a coordinating element between two opposite geometric entities: surface and perspective in depth. Let’s see to what extent the invention of perspective by Brunelleschi is of great importance at this juncture of science and art in which the new concept of space was created. The transverse arches (subarches) that support the sail vaults divide the interior of the porch into a series of sections that are in fact geometric cubes. Indeed: the springing line of the arches, the height of the columns and the distance between them have identical dimensions. The succession of these spatial cubes along an axis is a perfect architectural illustration of the “visual pyramid” of the theory of perspective (as is known, perspective assumes that the eye of the observer is located in the center of the base of the pyramid, and its vertex is the “vanishing point” towards which all the lines of the space converge). Thus, it turns out that each of the arches of this portico of the Hospital of the Innocents marks the intersection of a plane perpendicular to the optical axis with the visual pyramid. These surfaces that limit the succession of spatial cubes allowed Brunelleschi to demonstrate, as we said before, that the depth of space is reducible to the plane.

View inside Brunelleschi’s arcade (portico) of the Hospital of the Innocents, a crystal-clear example of the visual pyramid of linear perspective. The layout of this portico reveals a clean and clear sense of proportion in line with the mindset of the day: a new age with a high esteem for secular education and with a sense of great order and clarity appropriate for a clear-minded society.

Only now, with Cubism, it has been seen that not all space is reducible to the plane, because Brunelleschi’s brilliant approach is only valid when the viewer is not in the space, but in front of it, like a spectator who contemplates the stage from the stalls of a theater.

A Corinthian-composite capital of a column of the portico of the Hospital of the Innocents by Brunelleschi. The abacus is the flat slab between the starting lines of the arch and the capital per se.


Composite order: A mixed order, combining the volutes of the Ionic order capital with the acanthus leaves of the Corinthian order. The Composite order is essentially treated as Corinthian except for the capital, with no consistent differences to that above or below the capital. The Composite order is not found in ancient Greek architecture and until the Renaissance was not ranked as a separate order. Instead it was considered as an imperial Roman form of the Corinthian order.

Dihedral angle: The angle between two intersecting planes. In solid geometry, it is defined as the union of a line and two half-planes that have this line as a common edge.


Sail vault: One of the methods of developing a dome out of a square by taking the diagonal of the square as the diameter of the dome. In this case the dome starts as if by pendentives, but their curvature is then continued without any break. Such domes are called sail vaults, because they resemble a sail with the four corners fixed and the wind blowing into it.

Springing line (of an arch): A horizontal line between the springs of an arch or dome.