Architecture and symbolism of the Sagrada Família

Gaudí had an unflattering opinion of the Gothic cathedrals everyone admired: he said their flying buttresses were crutches. A building that needs external supports to keep from falling down, he argued, is a poorly resolved building. The Sagrada Família is, among other things, proof that he was right: it rises seventy-five meters on the inside and has not a single buttress.

What follows is how he did it. You don't need to know math to understand it; you need to look up with one idea in mind.

In a Gothic church, the columns are vertical. The weight of the vault doesn't come straight down, but diagonally, and that oblique force is what pushes the wall outwards: hence the buttresses, which redirect that force back to its place. Gaudí reversed the problem. Instead of correcting the outward thrust, he oriented each column in the direction in which the force wants to go down. A column tilted in this way only works under compression, which is what stone is good at, and it doesn't push anything sideways.

That's also where the branching comes in. A single column cannot support the weight of four separate vaults, so it divides into two at roughly halfway up, and those two then divide again, until each branch reaches just below the point it needs to support. The result looks like a forest because it functions like one: a trunk distributes the load onto branches, which in turn distribute it onto smaller branches. Gaudí didn't simply copy the shape of a tree for aesthetic reasons. He copied the solution.

The columns are not cylindrical either. Their cross-section changes with height: they start as a multi-pointed star and gradually rotate and increase the number of sides until they become almost circular at the top. The more weight a column supports, the more sides it has at its base.

Almost the entire basilica is made of a type of surface called ruled surfaces: curved surfaces that, surprisingly, can be generated by moving a straight line in space. This property is not a curiosity; it's the reason the building can be constructed: a ruled surface can be shaped, framed, and replicated using straight tools and taut strings. These are the four that you need to recognize, and where they are located.

The project includes eighteen towers, and they are not placed randomly; they form a hierarchy. There are twelve bell towers for the apostles, four on each facade. Four towers for the evangelists are located around the transept. One tower is dedicated to the Virgin Mary, situated above the apse. And in the center, the tallest of all, is the tower dedicated to Jesus Christ. The height of each tower indicates its position within that hierarchy, not the amount of funding allocated to it.

The bell towers are not the same, and the difference can be seen from the street if you know where to look. Those of the Nativity have twelve vertical ribs and start from a square base that gradually becomes circular. Those of the Passion have fourteen and start from a rhomboidal base that ends in an ellipse. Those of the Glory, when they exist, will have twenty and a decagonal base.

The oblique openings that run along the towers are not decoration: they are sound amplifiers, inclined stone panels that allow sound to escape downwards and prevent water from entering. Gaudí had planned to install 84 tubular bells in them, a giant carillon that does not yet exist. And the words written in mosaic along the shaft are also not mere decoration: they say Sanctus, Sanctus, Sanctus in three colors, yellow, red, and orange, one for each person of the Trinity, and below the pinnacle, Hosanna in Excelsis. Each tower also bears the initial of its apostle below the cross that tops it.

The facade of the Nativity faces the Marina street and is not perfectly smooth. It is organized into three portals: Hope, Charity, and Faith, and depicts the childhood of Jesus with hundreds of figures. Gaudí modeled these figures using molds of real people from the neighborhood and animals from nature, and for difficult poses, he used photographs with mirrors. Above the central portal, there is a stone cypress tree with white doves: the tree is a symbol of eternal life because it never loses its leaves, and the doves are the souls seeking refuge in it.

The facade of the Passion, on Sardenya Street, produces the opposite effect, and that was the intention. The six inclined buttresses that support it resemble tendons, the figures are angular and devoid of any ornamentation, and the stone is left bare. The sculptures are by Josep Maria Subirachs, who worked on them between 1986 and 2010, and who decided not to imitate Gaudí. It has divided opinions from day one, and it is worth knowing that the facade project itself is by Gaudí: what is not his is the sculpture.

The Facade of the Glory is the one that doesn's exist, and it's the main one. It faces Mallorca Street, looks towards the sea, and will tell the story of humanity until the final judgment. It has a structural peculiarity that is not repeated in the other two: the outer half of its towers does not extend all the way down to the foundations, but rather starts about thirty meters above ground, supported by eight columns placed at the edge of the plot. These eight columns represent the eight beatitudes. This is a typical idea of Gaudí: the number of supports is not determined solely by structural considerations.

The stained glass windows are not colored arbitrarily. They follow the orientation of the temple: blue and green on the east side, over the facade of the Nativity, and orange and red on the west side, over the Passion. In the morning, one side is illuminated, and in the afternoon, the other; the interior changes color temperature throughout the day. During the central hours, when the sun is high, the twenty-five skylights of the transept are responsible, letting in light from above through the hyperboloids.

There is a practical consequence that no description of the entrance mentions. In winter, the sun rises late, and the facade of the Nativity receives direct sunlight for just over an hour, most of which is before the basilica opens. The blue light of the morning is, for those who visit, a phenomenon that occurs mainly in spring and summer. The warm light on the side of the Passion, on the other hand, falls within the opening hours throughout the year.

At the corner of Sardenya and Provença, there is a structure that almost no one looks at, completed in 2017: the sacristy of the east. It has a square base of 18.55 meters on each side, a height of 43 meters, and is formed by twelve paraboloids that intersect each other. It has the exact same geometry as the central towers, but on a reduced scale. Gaudí designed it this way intentionally: he wanted to leave a structure built, in a manageable size, the solution that would have to be applied above a century later. If you wonder how they could have built the tower of Jesus Christ without complete plans, part of the answer is in that corner.