Gaudí moved from an initial neo-Gothic project to a personal and organic style, inspired by nature. He used columns in the shape of tree trunks to replace the Gothic buttresses, which not only offloaded the weight of the roofs to the ground in a practical way, but also created an interior space reminiscent of a forest. Construction began in 1987, with completion in 2010, and features a Latin cross plan with five main naves and a three-nave transept. The heights vary between 30 and 60 meters, and Gaudí based the entire structure on a 7.5-meter module, which he considered the ideal proportion.

The apse is lobed, with an ambulatory around the presbytery and seven chapels. Inside, there are 36 columns with bases on different sides and construction materials ranging from Montjuïc stone to granite. The vaults, in the form of hyperboloids, use the technique of vaulting with bricks and mortar. Symbolic details include stained glass symbols on the skylights of the vaults and the symbolism of the columns.

The interior has a deep religious meaning, representing different concepts such as the Way of Humanity and the Way of Jesus Christ. The naves represent the Church in its different states and the temple symbolizes the New Jerusalem. The columns have specific meanings, such as those dedicated to the evangelists and apostles.