A mountain system of south-central Europe, about 800 km (500 mi) long and 160 km (100 mi) wide, curving in an arc from the Riviera on the Mediterranean Sea through northern Italy and southeast France, Switzerland, southern Germany, and Austria and into the northwest part of the Balkan Peninsula. The highest peak is Mont Blanc, 4,808 m (15,774 ft), on the French-Italian border.