The 1966 flood of the Arno (Italian: Alluvione di Firenze del 4 novembre 1966) in Florence killed 101 people and damaged or destroyed millions of masterpieces of art and rare books. It is considered the worst flood in the city's history since 1557. With the combined effort of Italian and foreign volunteers alike, or ("Mud Angels"), many of these fine works have been restored. New methods in conservation were devised and restoration laboratories established. However, even decades later, much work remains to be done.