The River Elsa cuts northwards from its source in the hills west of Siena before joining the Arno. Colle di Val d’Elsa is the main centre along its Sienese upper reaches, noted for its glass industry. Some 95 percent of Italy’s lead crystal hails from here, and the lower town is crammed with shops selling its wares. The upper town is set along a winding ridge, and full of historic interest. Several museums showcase Etruscan and Sienese art.