During the Roman domination Calahorra was a city of the empire, Calagurris Iulia Nassica, and in the medieval period exerted enormous influence throughout La Rioja as episcopal see. Its cathedral was the first in the region. Later the diocese would experience various changes until receiving the current name, Diocese of Calahorra and La Calzada-Logroño, which has two more cathedrals, in Santo Domingo de la Calzada and in Logroño.
The Calahorra Cathedral, or Cathedral of Santa Maria, very close to the river Cidacos, is supposed to be built on the site where San Emeterio and San Celedonio -Roman legionaries converted to Christianity around the fourth century- were beheaded. Early religious pilgrimages to this point led to the creation of a Visigoth baptistery, which was destroyed during the Arab conquest. After the reconquest, a Romanesque temple was erected on the same site. The existing building was started in the late fifteenth century, in Gothic style, and was not completed until two centuries later, so it includes Renaissance and Baroque parts. No Romanesque remains are preserved.
The temple has a Latin cross layout and three naves. Outside, the most interesting features are the door of San Jeronimo, Plateresque; the main façade, sometimes described as Baroque and other times as neoclassical, and the tower. The interior deserves a relaxed visit, because it has many elements of artistic interest, such as the Gothic cloister, the sacristy and the choir. Among the many chapels, the main ones are that of the baptismal font, from the sixteenth century; the chapel of the Holy Martyrs, with a Baroque altarpiece and murals; and the chapel of San Pedro, which houses an impressive Plateresque altarpiece made of alabaster.
The cathedral was declared a national monument in 1931. Next to it is the Episcopal Palace, from the sixteenth century, a large building constructed in ashlar masonry, with no other adornment than a coat of arms on the façade.