The Pisuerga as it flows through Simancas Nature · Simancas, Campiña del Pisuerga, Valladolid Image of Simancas, not of the place itself. The river surrounds the walled hill and is crossed by the medieval bridge that inherited the course of a Roman road. The banks preserve groves of poplar and elm and are the natural passage between the moorland and the plain. Photo: Leofenix (CC BY-SA 3.0) What to see and do in Simancas