I learned a lot about this Catholic Church during a free tour I took with Running Bean. When Gaudi was building the Sagrada Familia, he knew it wouldn't be completed before his death. To keep his original vision in tact, Gaudi left explicit blueprints, 3-D models, and plaster molds that would help future architects finish the project. Unfortunately, during the Spanish Civil War, much of these preparations were destroyed.
The construction of the Sagrada Famila started in the late 1800s. However, after Gaudi´s death in 1926, construction stalled until the 1950s and is still going on today. In fact, it isn't projected to be finished until 2026!
There are three main sides (Nativity, Passion, and Glory) of the Sagrada Familia, all of which depict the story of Jesus Christ. When it is fully constructed, there will also be eighteen spires. Twelve of these spires will represent the Apostles, four for the Evangelists, one for the Virgin Mary, and lastly Jesus Christ, which will be so tall that it will be seen all throughout Barcelona. As for the interior, Gaudi used innovative techniques. The most notable are the tree-like columns, that give the church the support it needs.