Dominating the eastern end of Plaza del Pilar, La Seo is Zaragoza's finest work of Christian architecture, built between the 12th and 17th centuries and displaying a fabulous spread of styles from Romanesque to baroque. It stands on the site of Islamic Zaragoza's main mosque (which itself stood on the Roman forum's temple site).
La Seo's northeast external wall is a Mudéjar masterpiece, deploying classic brickwork and colourful ceramics in complex geometric patterns. Inside, beautiful fan vaulting adorns the ceiling while the numerous elaborate chapels, framed by encrusted stonework, ring the changes from the eerily solemn Capilla de San Marcos to the golden baroque baldachin of the Capilla del Santo Cristo. The exquisite 15th-century alabaster high altarpiece is well worth scrutiny too. The attached Museo de Tapices houses a collection of Flemish and French tapestries considered the best of its kind in the world.