eastern part of the Pyrenees consists largely of granite and gneissose rocks, while in the western part the granite peaks are flanked by layers of limestone. The massive and unworn character of the chain comes from its abundance of granite, which is particularly resistant to erosion, as well as weak glacial development. The upper parts of the Pyrenees contain low-relief surfaces forming a peneplain. This peneplain originated no earlier than in Late Miocene times. Presumably it formed at height as extensive sedimentation raised the local base level considerably. Landscape Conspicuous features of Pyrenean scenery are: the absence of great lakes, such as those that fill the lateral valleys of the Alps the rarity and relative high elevation of usable passes the large number of the mountain torrents locally called gaves, which often form lofty waterfalls, surpassed in Europe only by those of Scandinavia the frequency with which the upper end of a valley assumes the form of a semicircle of precipitous cliffs, called a cirque. The highest waterfall is Gavarnie (462 m or 1,515 ft), at the head of the Gave de Pau; the Cirque de Gavarnie, in the same valley, together with the nearby Cirque de Troumouse and Cirque d'Estaubé, are notable examples of the cirque formation. Low passes are lacking, and the principal roads and the railroads between France and Spain run only in the lowlands at the western and eastern ends of the Pyrenees, near sea level. The main passes of note are: Col de la Perche (), towards the east, between the valley of the Têt and the valley of the Segre, Col de Puymorens (), on European route E09 between France and Spain. The nearby he Pas de la Casa or Port d'Envalira, the highest road pass in the Pyrenees at , and one of the highest points of the European road network, which provides the route from France to Andorra, The Port de la Bonaigua (), in the middle of the range at the head of the Aran Valley. Plan de Beret () Col du Pourtalet (). The Col de Somport or Port de Canfranc (), where there were old Roman roads. Col de la Pierre St Martin () Puerto de Larrau () The Roncevaux Pass (), entirely in Navarre (Spain) is an important point on the Camino de Santiago pilgrimage route. Because of the lack of low passes a number of tunnels have