The Cathedral of Santiago de Compostela is the most visited religious destination in Spain. The Leon Cathedral, The Holy Grail in the Cathedral of Valencia, Spain, The Sagrada Familia in Barcelona and Mosque at Cordoba are the other most famous religious places in Spain. La Sagrada Familia is a perfect example of Art Nouveau architecture and the edifice is also filled with countless examples of religious symbolism. The interior of the cathedral is also awe-inspiring. Mezquita de Cordoba.