This natural depression in the center of the region was carved by river Ter and its tributaries and makes up a big part of Osona's land. It is completely surrounded by mountains: The Sub-Pyrenees, with Bellmunt mountain towering in the north, the Lluçanès (Pre-Pyrenees) to the north-west and Moianès high plateau in the West, the Montseny in the southeast and the Guilleries, located at the apex of the Catalan Transversal Range and the Pre-Coastal Range, in the east.