The terrain is almost entirely mountainous, except for a narrow strip along the upper Adige River, where most of the population is concentrated. The region includes the Tyrolean Alps south of the Brenner Pass and, in the east, part of the Dolomites. The region is divided into Trento and Bolzano provinces. The provincial capitals alternate biennially as the site of the regional parliament. The provinces have considerable autonomy. Most of the inhabitants of Bolzano province, and roughly 40% of the total population of the region, are German-speaking; the rest speak Italian or, a tiny minority, Rhaeto-Romanic. Agriculture forms the backbone of the regional economy, with cereals, fruit, and dairy cattle the principal items. There is mining of zinc, lead, copper, and iron. There is also a large tourist industry, in both summer and winter.