Sondrio is an Italian city, comune and administrative centre for the province of Sondrio, located in the heart of the Valtellina. As of 2015, …Sondrio is an Italian city, comune and administrative centre for the province of Sondrio, located in the heart of the Valtellina. As of 2015, Sondrio counted approximately 21,876 inhabitants. In 2007, Sondrio was named the Alpine Town of the Year.