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).