Slow Movements along the slip surface of the 1900 Porta Cassia landslide in the clayey slope of theOrvieto Hill

The largest documented landslide ever to have occurred in the clayey slope of the Orvieto hill is described with reference to a geotechnical framework of the hill. The evolution of the movements which are still under way along the sliding surface one hundred years after the landslide event is illustrated and its correlation with piezometric level changes as well as with rainfall is discussed.