colle di val d'elsa or colle val d'elsa is a town and "comune" in tuscany, italy, in the province of siena. it has a population of c. 20,000 inhabitants (2005). its name in italian means "hill of elsa valley", where "elsa" is the name of the river which crosses it. today, colle di val d'elsa is internationally renowned for the production of crystal glassware and art, largely produced in the industrial lower town.