The coast, particularly at the western tip, is irregular and rocky, with natural harbors (notably at Brest, Lorient, and Saint-Malo) and numerous islands. Important rivers include the Odet and Vilaine. The emigration of the young has resulted in a serious decline in the region's population. Brittany and the Breton people have retained many old customs and traditions. Breton, their Celtic language (akin to Welsh), is spoken in traditionalist Lower (i.e., western) Brittany outside the cities (see Breton literature). Brittany has remarkable stone calvaries, some built at the close of the 16th cent. to ward off the plague. Many megalithic monuments, formerly ascribed to the druids, dot the Breton landscape, notably at Carnac. These sights and the local traditions (old-fashioned peasant dress and high lace headgear, processions, and pilgrimages), which its inhabitants jealously maintain, have made Brittany an outstanding tourist attraction.