Florence Cathedral, Santa Maria del
Fiore, was built by Arnolfo di Cambio, an architect from the gothic period in Italy.
He was such a good architect that he had great ambitions for the Cathedral, and he would
conceptualize a giant dome, the biggest dome that anyone had ever built before, even bigger
than the illustrious dome of the Pantheon in Rome. So Florence is going to have a great
looking church, Arnolfo knows how to do it, he builds a lot of it and then he dies, and
nobody had a clue how to build the dome. It was not until a century after Arnolfo’s
death that someone submitted a model of a promising solution to the construction
of the dome: Filippo Brunelleschi. Brunelleschi's training was not as an architect and not even as
a sculptor, but as a member of the silk guild, he's a goldsmith, so he's got some expertise
in casting metals, but he has no expertise at all in architecture, however, he went to Rome
for a couple years to study the ancient ruins of the Romans, and he did not rest until there
was no sort of building he had not sketched: round, and square temples, basilicas,
aqueducts, baths, arches, amphitheaters, and every kind of brick temple, extracting
from all this the methods employed in girding and securing the walls and in constructing the
arches of the vaults, as well as the means of joining stones by hinging and dovetailing.
As I mentioned before, there was this big problem for the city of Florence, and that was
when Arnolfo di Cambio died there was a giant octagonal hole in the middle of the church,
and Florence by this point had prospered sufficiently that they felt they should try to
get something on top of that giant gaping hole, and so they had a competition, and everybody was
invited to submit projects, and Brunelleschi, after coming back from Rome, came to the Board of
Overseers and said “I can do it, I can build you the dome, and what's more I can build you the dome
without coins or earth” and what he means is that the Dome of the Pantheon which was the exemplar
dome to which every other dome would be compared, was said to have been built on a mound of
earth, and the stones were laid up on this earth mountain, and then after the entire structure
was intact the earth was carried away by the citizens of Rome, who were happy to carry the dirt
away because cleverly as they were building this mound of earth they put coins in there. So the
Pantheon, probably not true, but the Pantheon was said to have been built with coins and earth.
So Brunelleschi says to the overseers, and this is according to Giorgio Vasari’s lives of the
artists. “I will not tell you how I will do it, because if I tell you, my method will be so clear
and so logical everyone will want to do it, but I will give you a demonstration of how clever I am,
and if you can do what I set forth as your task, then I will tell you my method for building
the dome”. And he proposed to both foreign and Florentine masters that whoever could stand an
egg up on its vertical axis upon a marble slab should execute the dome, since in this way their
intelligence would be revealed. All those masters tried to make it stand upright, but none of them
found the way to do it. Then they asked Filippo to do it, and he graciously took the egg, cracked its
bottom on the marble and made it stand upright. The artisans loudly complained that they could
have done the same thing, and, laughing, Filippo answered that they would also have learned how
to vault the dome if they had seen his model and his plans. And so they decided that Filippo should
have the responsibility of executing this project. So what Brunelleschi does is, he projects it
not as a singular dome, but a double dome, a thicker lower dome that is mainly structural,
which is holding the weight of the dome itself and the lantern, and on the other
hand an outer protection dome. So between the two domes there is an
empty space that allows to lighten the dome and release great weight while
keeping the thickness of the dome. When I talked about the Pantheon I mentioned
that the geometry of the coffers do something quite similar, the material is scooped away
through the coffering to make the dome lighter, and the coffers also begin to brace
the structure and make it stiffer. The space between the two domes also allows
accessibility to the top of the dome, the lantern. So there are many innovations that
Brunelleschi proposes with his dome. Structurally we know that the problem of
a dome, and I already talked about this when I talked about the Pantheon
and Hagia Sophia, is the thrust, the transmission of horizontal loads right in
the place where the dome rests on the lower wall. Now there were several ways to solve this problem,
one was to widen the wall a lot so that the thrust vector remained within the thickness of
the wall, which is what the Pantheon does, another was to rest the dome on pendentives
like in Hagia Sophia, and there was also the option of placing flying buttresses to take the
load out which is the typical Gothic solution, where it also uses pinnacles to put
weight on top to center the thrust load, but Brunelleschi can’t use any of these solutions
because one: the thickness of the wall is already established, and two: he can’t use pendentives
because he already has an octagonal plan, and three: the flying buttresses from the French
gothic is something that Italians just never used. So what Brunelleschi opts for is an
intelligent solution based on the fact that the dome has an empty space inside.
The part from the middle down is the part of the dome that tends to open due to the thrust, this
is producing tension, and brick withstands tension and bending very poorly, so what’s going to
happen is that the dome is going to crack, and if that crack is too big, the dome will collapse, it
will not be able to cope with those deformations. So how does Brunelleschi keep the dome from
deforming too much and how does he control this cracking due to the thrust? He places elements
that work as belts, these rings that are tying the dome from the outside as if they were belts like
the ones we wear, that are containing the dome, that are preventing it from deforming. Some of
them are made entirely of wood, and some of them are made of sandstone beams stuck together with
cramps of iron, and therefore, as these belts are elements whose material withstands tension
very well, they are going to be able to assume these deformations. These elements are placed
inside the dome, between the exterior and the interior layers, and they are the ones that make
it possible to solve the problem of deformation. You can actually see one of these
chains of stone beams from the exterior, and it’s this series of pegs that protrude
from the drum. They were originally meant to be covered by a wooden gallery like the one you
see on one of the sides, but Michelangelo said that he preferred to see how the structure
is working, so they left it unfinished. Now the main reason Brunelleschi got the
commission from the competition was the possibility of raising the dome without using
a wooden centering. In traditional construction in the Roman manner, the domes and vaults had
to be supported during the construction phase on an ancillary structure that was always made
of wood, a structure that could be very complex and that was only removed when the upper ring of
compression had been closed. That in a dome with a span of forty-four meters is much more complex, it
would have led to a very expensive centering that would also have to be supported about fifty-two
meters above the ground. Brunelleschi's solution consisted of completely disregarding the idea
of scaffolding by using a particular kind of brickwork, a pattern with a series of spiral ribs,
which are the ones you see here, separated by no more than one meter, which allowed them to lock
together the bricks that were placed horizontally. They had to be held together because of the
slope that the walls had as the dome grew. The result is that the structure was completely
self-bracing in all its phases of construction, from the beginning to the end, and therefore,
it did not depend on a scaffolding, it did not depend on an expensive wooden centering, so
this is the ingenuity of Mr. Brunelleschi. Now where did Brunelleschi get this
idea from, which is quite complex, because it implies understanding very
well how a dome of these characteristics is behaving from a structural point of view? Well,
he apparently got it from the Roman brickwork that was normally used either to cover the floor,
or to cover the walls with Roman concrete. And this is the space between the two domes, which
I personally think is fantastic, you can see every part of the structure here: the sandstone and
wooden chains that contain the dome from cracking, the spiral herringbone brickwork that was used,
and what’s more, you experience the curvature of the dome as you walk around it and climb
up the stairs that lead to the lantern. These are the same stairs that the construction workers
climbed every single day when the dome was built. When you visit the dome, you enter through
this door with this Latin inscription: ianua caeli, which can be translated as “the
door of heaven” or “the door of the sky”, and I think it’s a pretty good analogy because when
you get to the top, the view is just breathtaking, you’re in the highest spot in the city, and
you can see all Florence from that point. You can see some of the other buildings that
Brunelleschi designed like San Lorenzo down here, or Santo Spirito over there, and you can see other
important buildings like the Palazzo Vecchio and the Uffizi Gallery to the south, Santa Croce to
the southeast, Santa Maria Novella to the west, the Palazzo Medici to the north, and the Ponte
Vecchio over the Arno River. Another great sight is the Cathedral itself viewed from the top, you
can appreciate the bell tower and the baptistery very nicely from up here, and if you climb to
the top of the bell tower you’ll have the best view you can possibly get of the dome, and
you can see how massive a building it is. When you come down from the top of the dome, you
walk through the gallery around the interior dome, where you can see very closely and with great
detail the fresco on the ceiling made by Giorgio Vasari, who took inspiration from the Book of
Revelation along with Dante's Divine Comedy. The only obstacle that remained to be resolved,
other than the tremendous construction logistics that all this implied, was how to raise the
materials more than sixty meters to the top of the dome. To solve this problem, Filippo devised
a large wooden crane, very sophisticated for its time, and that allowed the materials to be raised
as the dome got taller by activating a pulley with animal force. This hoist caused admiration
among contemporaries and for many decades after Brunelleschi's death, in fact, we know how it
looked because Leonardo da Vinci drew it when he was young, working in the workshop that
built the bronze orb on top of the lantern. So the building of the dome is a project
that Brunelleschi worked on for years, beginning in 1418 when he submitted
his first model, and ending really at the end of his life in 1446. He lived long
enough to see the dome completed, however, even though he designed the lantern, it was
completed about 30 years after his death. Today, five centuries later, the dome still
dominates Florence, it can be seen from churches, terraces, balconies, anywhere in the city,
when you turn a corner it unexpectedly appears and whether you see it from far away or from
the piazza del duomo, it’s just an awe-inspiring sight. And the fact that it was built by men with
a limited understanding of the forces of nature, only makes it more of a wonder. I’m
sure Brunelleschi would be proud to know that next to the cathedral there is a
statue of himself looking at his creation. If you want to go deeper into the subject of the
dome I recommend you reading Brunelleschi's Dome by Ross King, he just goes so much into detail
about Florence, and about Brunelleschi's life, and about the construction of the dome, so in
case you're interested I'm going to leave a link in the description below. There are more
videos about Italy and about Florence to come very soon, so let me know in the
comments what would you like to see first. Don't forget to like this video, to
subscribe to my channel, it helps me so much. Thanks for watching, and I'll see you
very soon in another episode. Goodbye!
