Inside Sagrada Familia: what you'll see in the Basilica

The forest comparison is not accidental. Gaudí designed the columns to branch at different heights and carry the weight of the roofs and vaults down to the foundations, which let him do without the flying buttresses of Gothic cathedrals. The Basilica's own architectural documentation calls these columns "structural trees".

If you can choose your entry time, think about the light. Morning sun comes in from the east, through the cooler blue and green glass on the Nativity side. Later in the day the western Passion side glows with reds and oranges. The effect also changes a great deal with the season and the weather.

1. The branching columns, Gaudí's stone forest.
2. The coloured stained-glass light, cool on one side and warm on the other.
3. The ceiling and hyperboloid vaults: look straight up.
4. The central nave, one of the best perspectives inside.
5. The altar and the suspended Christ in the apse.
6. The columns' changing materials and colours.
7. The crossing beneath the central towers.
8. The inscriptions and symbolic details around the interior.
9. The organ and the choir galleries.
10. The museum, especially if you want to know how Gaudí designed the building.

This is the most important idea behind the interior. Gaudí did not decorate ordinary columns to look like trees. The tree shape is structural.

Most of the columns lean slightly; few stand perfectly vertical. Higher up they divide into branches, which spread the loads of the vaults, roofs, windows and central towers before carrying that weight down to the foundations. The Basilica's documentation describes the system as a series of tree-like structural columns branching at different heights.

That makes the interior far more interesting to look at. The forest is not a picture laid over an engineering system: the engineering itself makes the forest.

Inside, the Basilica is about 90 metres long.

What matters is what those numbers do as you walk. The vaults get higher as you approach the most important liturgical areas, so you feel the space opening upwards as you move through the church.

One of the best views inside is also the simplest. Find a spot along the central nave and look towards the altar. From here you can see:

• branching columns on both sides
• the rising vaults
• coloured light coming in from the sides
• the altar framed by the apse
• the build-up towards the central crossing

Then turn around and look back. The perspective changes completely.

Gaudí's structural system let him make the columns thinner than those in Gothic cathedrals and freed the walls from carrying so much load. That left far more wall for windows, and it gives you long views across the interior.

Don't spend the whole visit walking forwards. Some of the best views appear when you turn round.

A surprising number of visitors spend most of their time looking straight ahead. Look up instead: the ceiling is where the tree idea reaches its climax. The branching columns spread into a canopy of geometric vaults, with openings that bring extra daylight into the Basilica.

Gaudí used hyperboloid geometry to create skylights between the columns, and the Basilica's interior documentation counts 289 skylights bringing light in from above. That is one reason the church feels so much brighter than many old European cathedrals.

Gaudí admired Gothic architecture but thought its structure could be improved. Traditional Gothic cathedrals rely on external buttresses and flying buttresses to resist the sideways push of their vaults, which Gaudí saw as an imperfect solution.

At Sagrada Família he developed an internal system of inclined, branching columns that sends the loads down through the structure. That greatly reduced the need for huge supports outside, and it is one reason the inside feels so open.

The main nave has been enclosed and used for worship since Pope Benedict XVI dedicated it in 2010, but Sagrada Família as a whole is still an active construction project. Work has continued on:

• the central towers
• the Glory façade
• the Chapel of the Assumption
• sections of the cloister
• related architectural elements

The Glory façade, which will become the main entrance, is still to come, so the building as a whole is some years from completion.

The interior you visit is a working consecrated basilica, not an unfinished shell. Construction elsewhere on the site can still affect views, routes and which areas are open on the day.

Yes. Gaudí is buried in the crypt beneath the Basilica, in the Chapel of Our Lady of Mount Carmel. The crypt is older than most of the main Basilica and was one of the first parts of the church to be finished.

Don't assume an ordinary sightseeing route gives you access to every part of the crypt. Access depends on religious use and current visitor arrangements, so if seeing Gaudí's tomb matters to you, check the current conditions before you go; it is not a guaranteed stop on the normal route.

After an hour of finished architecture, the museum shows how on earth it was designed. It is especially rewarding if you are interested in Gaudí's working methods. Instead of relying only on flat drawings, he used:

• physical models
• geometric experiments
• hanging-chain models
• photographs
• three-dimensional design methods

Once you have seen the real columns and vaults, models that might have looked technical suddenly make sense. Allow at least 15–30 minutes if architecture interests you.

With a phone or a normal camera, the practical advice is simple:

• don't bring a tripod
• don't stage a professional photo shoot
• don't block other visitors
• remember you are inside a working church

For a first visit, yes. If your Barcelona budget makes you choose between seeing the outside for free and buying a Basilica ticket, we would put the money on the interior. The façades are astonishing and you can see them from the public streets, but they don't prepare you for the change inside: dark sculpted stone gives way to light, colour and enormous open space. Judging Sagrada Família from exterior photos alone gives a misleading idea of the building.

The towers are an optional add-on, and the nave is the essential Sagrada Família experience. A tower gives you unusual architecture and views, but the interior is where the building's central ideas are clearest. Our Sagrada Família towers guide covers how the tower visit works if you are weighing it up.

1. Stop shortly after entering. Don't start listening, photographing and walking all at once: look across the whole nave first.
2. Take in the Nativity-side light and its cooler colours.
3. Follow one column upwards and find where the shaft branches.
4. Walk to the crossing and look straight up when you reach it.
5. Pause in front of the altar to see the Christ, the baldachin and the apse.
6. Cross to the Passion side and compare its warmer glass with the Nativity side.
7. Walk back through the nave for the reverse perspective.
8. Visit the museum after the architecture, not before, so the models are easier to understand.

Even on a normal sightseeing day, Sagrada Família has an interesting acoustic. Gaudí built in raised choir galleries and designed the interior with liturgical music in mind, and the Basilica's architects have explained that the vault geometry helps carry singers' voices through the space. It also means visitor noise travels, so keep your voice low.

• The changes in column stone. The different colours are not just the lighting.
• The clear upper windows. Look above the brightly coloured glass.
• The column knots, where the trunks begin to branch.
• The choir galleries, part of Gaudí's acoustic design as well as the visual one.

• The plain altar, much simpler than the architecture around it.
• The reverse view. Turn round every so often.
• The museum, especially easy to rush if you have already been inside for an hour.

1. spend the first few minutes just looking around the nave
2. compare the cool and warm sides of the stained glass
3. follow several columns from floor to ceiling
4. stand under the crossing and look straight up
5. spend time at the altar and apse
6. walk back through the nave instead of leaving straight away
7. finish in the museum

And we would resist photographing every metre of the building. The interior makes much more sense once you stop treating it as a series of Instagram angles and start looking at how the columns, light, stone and geometry work together.

Still deciding how to book? Our Sagrada Família tickets guide compares every official ticket, and the guided tour vs ticket comparison covers when a guide is worth it.