The 240-km-long River Arno winds its way seaward through the tranquil countryside of Umbria and Tuscany, but this tranquillity masks potential danger. There are more than 300 areas within Italy’s Arno Basin at high risk of landslides, and over 20 000 individual landslides have been recorded.
More at:
http://www.esa.int/export/esaEO/SEM5GPRMD6E_environment_0.html