Its area is approximately 8,694 square miles (22,520 km2), with a population in the early 20th century of 340,000, divided into 1220 parishes which form forty-seven vicariates.

The mountainous region is unproductive of cereals, but fruits grow in abundance, and fine pasture-lands sustain great herds of cows and sheep, which furnish excellent meat and milk.

Although this section has few industries, the transportation of its fruit and minerals is greatly facilitated by the numerous highways and by the railroad between Madrid and France which crosses the eastern side of the diocese from south to north.

Another national council, presided over by Cardinal Boso (d. 1181), also papal delegate, settled questions of discipline and established diocesan rights and limits.

In 1898, a provincial council was called by Archbishop (not Cardinal) Don Gregorio Aguirre, in which the obligations of the clergy and the faithful were most minutely set forth.

Among its saints may also be mentioned the martyrs of Cardeña, religious of the convent of the same name, who in the tenth century were executed by the Arab soldiers of the Emir of Córdoba in one of their numerous invasions of Castile; and St. Casilda, daughter of a Moorish king of Toledo, converted near Burgos whither she had gone with her father's consent to drink the water of some medicinal springs.