The Pisuerga as the boundary between two provinces Nature · Itero del Castillo, Odra-Pisuerga, Burgos Image of Itero del Castillo, not of the place itself. The river marks here the boundary between Burgos and Palencia. It is crossed by the bridge of Itero, also called de la Mula, a long ashlar bridge that the Camino Francés uses to leave the lands of Burgos. Photo: Timiotatongenos (CC BY-SA 3.0) What to see and do in Itero del Castillo