Barcelona, Spain (CNN) -- Pope Benedict XVI on Saturday began his second visit to Spain, where he prayed at the tomb of an apostle and planned to consecrate one of Barcelona's most famous sights -- the distinctive Gaudi-designed Sagrada Familia church.
The pope's first stop on his two-day trip is Santiago de Compostela, in Spain's northwestern tip, an important pilgrimage site for centuries.
The cathedral there was built 900 years ago atop what is said to be the tomb of St. James, an apostle of Jesus. After praying there, the pope presided over a Eucharist in the square outside, to celebrate the city's jubilee year.
"I come as a pilgrim on this Compostelean Saint Year ... I want to join to that long line of men and women that all over the centuries had come to [Santiago de] Compostela from different places on the peninsula and Europe," the pontiff said at the airport earlier in the day.
Saturday night, the pope planned to head all the way across Spain to Barcelona, the Catalan city on the Mediterranean.
Barcelona is home to the Sagrada Familia, or "holy family," church, still being built after more than 100 years. Benedict is expected to designate the church a basilica, a special honor in Roman Catholicism.
Antoni Gaudi, a Catalan architect, only lived to see one tower and most of one facade finished by the time he died in 1926.
"The interior space of the church, the sacred space of the church, is finished, and for that, the pope comes here to consecrate the church," said Jordi Fauli, the deputy architect.
Gaudi planned the church to have 18 towers -- 12 for the apostles and the tallest for Jesus. Only eight are finished.
Fauli said the privately-financed work may be done by 2026, on the 100th anniversary of Gaudi's death.
Asked once why it was taking so long to finish the Sagrada Familia, Gaudi replied, according to his assistants, "My client -- meaning God -- is not in a hurry."