"Gaudi devoted his life to God," Gabriela González-Cremona told me, a lawyer who is working with the Association of the Beatification of Antoni Gaudi. "He honored God by means of prayers and his masterpieces. Both his life and his work give testimony and intensify the faith to whoever contemplates them."
The process of beatifying Antonio Gaudi was initiated in 1992, as a group of religious figures, architects, canonical lawyers, and other followers began the campaign, embarking upon what is essentially a mountain of paperwork. In 1998, local bishops gave their approval to move the campaign forward. In 2003, the process was officially initiated at the Vatican. The campaign has now created a publication which outlines Gaudi's life and major works, and documents the entire beatification process up until this point.
Like you'd expect, sainthood, or canonization, doesn't come easy. In the Catholic Church, it's actually a three-step process, with a person named first as Venerable, then Blessed, then full-on Saint. The level of blessed (beatification) requires evidence of one miracle. To achieve sainthood (canonization), the church needs proof that the person in question has performed two miracles. (Martyrs—those who gave their lives for the church—only need one miracle total, which makes total sense.)
The miracle-proving is arduous. "It's not the hardest part but the most laborious of the process, because the Vatican is strict and requires the deep study of experts who can demonstrate that the miracle has been made without a scientific explanation," says González-Cremona. Essentially there is a Vatican panel of lawyers and medical experts whose jobs are to examine the miracles and determine that there is no possible scientific basis for how those miracles could have been performed. As you might guess, this has become a bit more difficult lately. Mother Teresa was beatified in 2003 but her second miracle has yet to be confirmed, so she's no saint (yet). Plus, the church has been criticized in recent years for relying too much on medical miracles—lots and lots of evaporating kidney stones in there—and not enough on miracles of the contemporary age.
When it comes to Gaudi, the association has been busy collecting hundreds of testimonies which could be offered up to the Vatican for miracle consideration. According to the documentation provided to me, these are stories from people who have prayed to Gaudi to help them with problems ranging from unemployment, to creative inspiration, to health issues, and have seen results.