It is bounded on the north-west by the province of Cantabria, north-east by the province of Biscay, south by La Bureba, south-east by Ebro, south-west by Páramos, and on the east by the province of Álava.
This area is surrounded by the provinces of Cantabria to the northwest, Biscay to the northeast, La Bureba to the south, Ebro to the southeast, Páramos to the southwest, and Álava to the east.