In 813 ce a tomb discovered at nearby Padrón was said to have been supernaturally revealed to be that of the apostle St. James, martyred at Jerusalem about 44 ce. His bones had been taken to Spain, where, according to legend, he had formerly evangelized. The discovery of the relics provided a rallying point for Christian Spain, then confined to a narrow strip of the northern Iberian Peninsula (most of the remainder of which was occupied by Moors). Alfonso II of Asturias built a church over the tomb, which Alfonso III replaced by a larger structure, and during the Middle Ages the town that grew up around it became the most important Christian place of pilgrimage after Jerusalem and Rome. The whole town, except the tomb itself, was destroyed in 997 by Abū ʿĀmir al-Manṣūr (Almanzor), military commander of the Moorish caliphate of Córdoba.

In 1078 the present cathedral was begun by order of Alfonso VI of Leon and Castile. This Romanesque building, located at the east end of the Plaza del Obradoiro, has a Baroque west facade (the Obradoiro) built (1738–50) by Fernando Casas y Novoa. An outstanding feature of the interior is the Pórtico de la Gloria, a tripartite porch located behind the facade and showing a Last Judgment sculptural composition by Maestro Mateo; the work is Romanesque but tinged with Gothic features.

To the north of the Plaza del Obradoiro is the Royal Hospital (now a hotel), which was built in 1501–11 by Enrique de Egas to receive pilgrims. Other noteworthy secular buildings are the colegios (“schools”) of San Jerónimo (founded 1501), Fonseca (founded 1506), and San Clemente (founded 1602) and the University (founded 1501, though the building dates from 1750). The Monastery of San Martín Pinario, now a seminary, was founded in the 10th century and rebuilt in the 17th. The Monastery of San Francisco was supposedly founded by St. Francis of Assisi when he made a pilgrimage to Santiago in 1214. The Church of Santa María Salomé and the collegiate Church of Santa María la Real del Sar in the suburbs both date from the 12th century, with later facades. Santiago is well known for its rúas (“narrow streets”), which surround the cathedral and add medieval charm to the historic center. The Cathedral Museum contains sculptures and Flemish tapestries, and the Galician People’s Museum is an ethnographic and anthropological museum. The Galician Centre of Contemporary Art was designed by the architect Álvaro Siza and houses Galician and international artistic creations.