and Valence is the most populous city. Valence was previously part of two intercommunalities: (Intercommunal Union of Services of the Valentinoise Agglomeration, better known under the name of "Valence Major") which includes seven Drôme and Ardèche communes (Bourg-lès-Valence, Cornas, Guilherand-Granges, Portes-lès-Valence, Saint-Marcel-lès-Valence, Saint-Péray and Valence) from 1990 to 2009, and of the agglomeration community of which consisted of eleven communes from 2009 to 2014. Neighbouring Communes Relief and geology The area of the commune is , representing ; the altitude varies between . The granitic base, cut by the Rhône in the Saint-Vallier/Tain-l'Hermitage pass, is covered by of sediments in the Valence trough. In the Miocene, a molasse formed of detrital rocks due to the erosion of the Alps and the Massif Central, was deposited in a shallow sea. Its thickness can reach . During the Pliocene, the sea was reduced into a lake, resulting in lacustrine deposits and loess formation. During the Quaternary, between glacial periods, moraines were swept away by the meltwater in the interglacial stages and were carved by the rivers. Thus, nested terraces were formed. These nested terraces of Isère and Rhône eventually filled the gap of Valence. The Drôme des Collines, which integrates Valence, formed at the end of the Miocene. Under the effect of the Alpine thrust, the area was covered by a lake and fluvio-lacustrine molasse formed with a few ripples in the plain of Valence. The confluence of the Isère and Rhône and fluvial erosion caused by their waters, in the Quaternary, formed four superimposed terraces which are located in Valence. Hydrography Valence is watered by the Rhône river, the commune is on the left bank. One of its tributaries also crosses the city: The , a -long river, formed by the joining of most of the city's channels, among others. Plain of Valence The city gave its name to a well-defined geographical region: The Valentinois. Over more than three-quarters of its territory, this region corresponds to the plain of Valence, shaped by successive beds of the Rhône which are abandoned fertile sedimentary deposits. Indeed, this plain, perfectly bounded by the Rhône Valleys to the west, the Isère in the north, and the Drome to the south, gives the appearance of a cheerful orchard with peach, apricot and cherry trees, alternating with cereal and vegetable crops. Large farms, conquered one by one by the inhabitants of Valence, punctuate this agricultural area, barely