This cathedral grew and changed with the city -- that is, until about the 18th century. Founded by a medieval queen and designed in a foreboding, basically Romanesque style, it's now a monument to changing architectural tastes. Part of the twin towers, the rose window, the naves, and the vestry are elements of the original 13th-century structure. The austere Gothic cloister was added at the end of the 14th century and later decorated with azulejos (tiles) depicting events from the Song of Solomon. Opening off the cloister is the Chapel of St. Vincent, built in the late 16th century.

The main chapel was erected in the 17th century, and in 1736 the baroque architect Nicolau Nasoni of Italy added the north facade and its attractive loggia. Twisted columns flank the monumental altar, and the nave is adorned with fading frescoes. In the small baroque Chapel of the Holy Sacrament (to the left of the main altar) is an altarpiece fashioned entirely of silver. The work is so elaborate that the whole piece gives the illusion of constant movement.