Banks of the Duero in Alconaba Nature · Alconaba, Frentes, Soria Image of Alconaba, not of the place itself. Twenty-one hectares of the municipal district are included in the Natura 2000 site Banks of the river Duero and tributaries, a corridor of alders, willows and ash trees that crosses a territory otherwise flat and given over to cereal. Photo: Miguel Ángel García. (CC BY 2.0) What to see and do in Alconaba