Limburg consists largely of sandy soils on the surface in the north. The Maas flows the entire length from south to north through the province and has incised the sand and gravel deposits of the Rhine. The Limburgs Heuvelland in the southeast is often labeled as Mergelland. The best known parts of the Mergelland are the Plateau van Margraten, which is bordered on the north by the valley of the Geul, and on the west by the Meuse valley with on the other side the Sint Pietersberg, on the east by the valley of the Gulp with the in the village of Gulpen and a little further up the heights around the Vaalserberg and south through the Voer region.