The riverside plain. It is the natural market garden and granary of the Basques. It is made up of a territory that stretches from the left bank of the Ebro, starting in the southern foothills of the Toloño mountain range, in the Conchas de Haro and the edges, also in the south, of the last series of sub-Pyrenean mountain ranges. From the vertex of this acute angle formed by the aforementioned mountain range and the Ebro, the plain becomes flatter and wider until it covers the lower part of the basins of the great rivers of Navarre and all of some of the streams that are direct tributaries of the Ebro. La Ribera approaches Estella by crossing the Ega, passes over Artajona after having cut through the Arga that flows down from Pamplona and continues to the north of Tafalla, bordering Ujué and Sangüesa. This extensive plain is far from homogenous. There are slight plateaus or moorlands, dry, ochre and grey lands, thinned out with olive trees, along the lower basins of the Ega, Arga and Cidacos. Olite, Eriberri, is the culmination of this type of relief. Further east, it reaches higher altitudes and more precise contours. To the south, in the heart of the Basque Country, from the mouth of the Aragón, in Milagro, a new steppe and desert area appears, whose mounds can be seen in full collapse, scorched by the sun. These are the Bardenas, delimited by the left bank of the Aragón and the Ebro, but which continue on Aragonese land. On the other side of the Ebro, the mountainous foothills of the Aragonese Moncayo reach its banks, penetrating Basque land from south to north in what we call the Zierzo mountains Fitero, Cintruénigo and Corella on one side and Monteagudo, Cascante, Urzante, Murchante and Tudela on the other.
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