TL;DR
The interior of the Sagrada Família is a 45-metre-tall forest of branching stone columns bathed in coloured light from hundreds of stained glass windows. Blue and green glass lights the east side in the morning; red and amber fills the west in the afternoon. The columns require no flying buttresses — Gaudí's structural innovation distributes load through branching geometry alone. Standing inside is the most powerful architectural experience in the world.
Why Do the Columns Look Like Trees?
Gaudí designed the columns to function exactly like trees. They branch at the top to distribute weight across multiple paths, exactly as a tree trunk branches into limbs, branches, and twigs. This structural system — which he derived from studying trees, bones, and shells in nature — eliminates the need for flying buttresses that support traditional Gothic cathedrals from the outside.
The result is a building that supports itself entirely through internal geometry. Engineers who validated Gaudí's calculations using modern computers in the 1990s found that his intuitive structural system was close to perfect. He had worked it out a century earlier using hanging chain models and physical intuition.
The columns themselves spiral as they rise — each one a different geometric spiral depending on its position and load. This is not decorative. The spiralling distributes forces evenly through the stone cross-section, making each column more resistant to both vertical and lateral loads. It's engineering expressed as beauty, which is what all of Gaudí's work ultimately is. A guided tour explains this system in detail with examples.
The Stained Glass: A Symphony of Colour
East Side (Nativity)
The east-facing stained glass was designed by Joan Vila-Grau in blues and greens to evoke the colours of the Mediterranean and the freshness of early morning. Morning visits get the full benefit.
West Side (Passion)
The west-facing glass burns red and amber in afternoon light. The colours intensify as the sun moves lower. Late afternoon on the west side of the nave is one of the most dramatic light experiences in any building.
The Stained Glass in Detail
The Sagrada Família's stained glass is not decorative in the traditional sense. It is a functional component of the building's spiritual and spatial programme. Gaudí specified the colour zones but died before the glass was installed; the work was completed by artist Joan Vila-Grau beginning in the 1990s, working from Gaudí's colour notes and the existing window apertures.
The east-facing windows use blue, green, and yellow glass in layers of varying density, creating different tones depending on the angle of sunlight. At 9:00 AM in summer, the light through these windows produces a deep aquamarine that fills the entire east nave — an experience that photographers travel specifically to capture. The colour cools and fades as the sun moves overhead.
The west-facing windows work in reverse: dim and cool in the morning, they ignite in the afternoon as the sun swings toward them. By 4:00 PM, the west nave is saturated with red, amber, and gold that intensifies until closing time. The contrast with the east side — visible simultaneously if you stand at the nave crossing — is one of the most extraordinary colour experiences in any building on earth.
Above both sets of side windows, the high clerestory windows use white and pale gold glass, representing divine light beyond earthly colour. This vertical transition — from earth-toned blues and reds at the sides to transcendent white above — was part of Gaudí's theological programme. Read more about the full symbolism of the building to understand the complete colour language.
The Nave Geometry — Why the Space Feels the Way It Does
The nave of the Sagrada Família has a Latin cross plan — a central nave with two side naves and a transept crossing — but this traditional footprint conceals a radical spatial logic. The central nave is 45 metres tall. The side naves are 30 metres. The crossing dome rises to 60 metres. These proportions, combined with the complete absence of walls (the space between columns is open glass), create a volume of light unlike any conventionally enclosed cathedral.
The ceiling is not a single vault but a series of hyperbolic paraboloid surfaces — saddle-shaped geometries that allow natural light into the nave through their complex curves. The starbursts of light visible in the ceiling are where these paraboloid surfaces intersect and are pierced by circular skylights. Gaudí designed over 400 individual ceiling elements, each a different geometric form.
Standing at the nave crossing and looking upward is the recommended moment for first-time visitors. The geometry of the ceiling, the branching columns, and the coloured light all converge at this point in the building. It is the moment most visitors describe as the most powerful architectural experience of their lives. Learn what else to expect during your visit.
The Column System — Four Types of Stone, One Structural Logic
Gaudí used four different types of stone for the interior columns, each chosen for its compressive strength and visual effect. The innermost columns — those carrying the highest loads from the central nave and crossing dome — are porphyry, one of the hardest natural stones. Moving outward, basalt columns carry intermediate loads. The outer columns are stone from Montjuïc. Brick columns appear in the exterior chapels.
The colour of the stone is structural information. The dark porphyry columns at the crossing are visually heaviest — you can read the load hierarchy by looking at the palette of the building. This integration of structural necessity and visual communication is characteristic of Gaudí's mature design method.
Each column spirals as it rises — some to the left, some to the right, at varying helical rates. This is not decorative repetition. The direction and rate of twist is calculated to counterbalance torque forces in the branching superstructure above. When a branching column divides, the branches go in opposite directions; the twist in the trunk below is designed to counteract the torsional forces created by this splitting. It is one of the most sophisticated structural solutions in the history of architecture.
Column Stone Types
Porphyry
Crossing (highest load)
Basalt
Central nave
Montjuïc stone
Outer nave
Brick
Chapel apses