Possibly Cebreros, 43 km southeast of Avila. Or, going strictly by the text, an unidentifiable town in Galicia.
To Don Alfonso he gave the kingdom of Leon, and in Asturias as far as the river Deva, which runs by Oviedo, and part of Campos as far as Carrion and the river Pisuerga, with the border, which contained the dioceses of Zamora, Salamanca, and Ciudad Rodrigo, and the city of Astorga, and other lands in Galicia, with the town of Zebreros.