Alarcia is a town of northern Spain, Autonomous Community of Castile and León, province of Burgos, Shire of Montes de Oca, sub-shire of Tirón-Rioja Burgalesa, in the municipality of Rábanos.

It lies between the reservoir Úzquiza (west) and the peak of San Millan (2,131 m) in the Sierra de la Demanda (southeast).

On arrival of the Romans in this area (1st Century AD), It belonged to the territory of Autrigones tribe.

The current shire of Montes de Oca, where is Halariza, Alariza or Alarcia, was repopulated mainly by Astur, Cantabri, Visigothic and Vascones (Basques) origins in the mid-ninth century, although remained border between the County of Castile with the Caliphate of Córdoba and its allies for at least a century.

[1] Between the 134 villages belonged to the alfoz of Cerezo, appears Halariza next to Valmala and Sancta Crux del Valle (Urbión).