Work was begun on the breathtaking masterpiece envisioned by Catalan architect Antoni Gaudi in 1882, and now 133 years after the first stone was laid, the architects are ready to embark on the final phase.
With work on 70 percent of the building complete, chief architect Jordi Fauli on Wednesday outlined plans for the final stage; raising the central tower that will surpass even the height of Germany's Ulm Minster to make it Europe's tallest religious building.
"The central Tower of Jesus Christ will be 172.5 metres (566 feet) tall, making it the tallest cathedral in Europe, because the tallest church tower in Europe is Ulm, at 162 metres (531.5 feet)," Fauli said in a press conference on Wednesday.
The central tower will be the tallest of six spires and will complete a structure that despite being unfinished is one of the most popular tourist attractions in Spain, drawing in more than three million visitors a year.
Fauli confirmed that the project is on schedule to have the building work finalized by 2026 in time to mark the 100th anniversary of the death of Gaudi, who was crushed beneath a tram in the Catalan capital at the age of 73.
He was so impoverished by the time of his death that he was mistaken for a tramp and laid unidentified in the city morgue for several days.
The finishing touches to the ornamentation covering the basilica, which was consecrated by Pope Benedict XVI in November 2010, could take even longer.
"It's difficult to predict but we can say that it will be completed by 2030, 2032," Fauli said at the press conference.
The project has been plagued with difficulties, including the destruction of Gaudi's original plans in a fire set by anarchists during the Spanish Civil War.
Gaudi, who is referred to as "God's Architect" and who is the subject of a petition for beatification, expected his "cathedral of the poor" to take two centuries to construct.
"My client is in no hurry," he famously said, referring to God.
When Gaudi was once asked why he was bothering to make the details at the tops of the spires so elaborate when they wouldn't be visible from the ground, he responded: "The angels will see them".
The entrance fees finance the construction budget of around €25 million ($28.38 million) a year.