The original Church was built by the King Alfonso the 5th over the ruins of poor materials and was devoted to Saint John the Baptist. It was rebuilt in stone in the Romanesque style by the King Fernando the 1st and the Queen Sancha under the patronage of Saint Isidoro whose remains arrived here in 1063. Afterwards was enriched by the Queen Sancha Raimundez in the 12th Century.
The floor is laid out as a Latin cross with one central nave, and 3 chapels, the main is taller in order to have light. The original header of the 12 th Century has two absides.
The main chapel was rebuilt in the gotic style by Juan de Badajoz the Older. The main altarpiece has the remains of Saint Isidoro inside a silver casket med in the 19th Century by Rebollo.
Calls our attention the the arches on the crossing of the transept hark back to Islamic art. However the many styles merge into a harmonious whole.
Outside, the “Puerta del Cordero” is one of the basilica's most notable features. Its name comes from the “Agnus Deis”. Coming through this door pilgrims of Santiago are forgiven sins. Other elements are the Zodiac and the figure of Saint Isidoro on horse.
The Basilica has a privilege since time inmemorial to have the Blessed Sacrament ever exposed.