Casco dell'Acqua is a little knot of houses in the frazione of Matigge, north-northwest of Trevi, at the bottom of the valley, bordering on the township of Foligno.

The name, meaning "Falling of the Water", derives not from a waterfall properly speaking, but from a drop in the waters of the Clitunno river due to a manmade weir: at which point the "Canale dei Molini di Montefalco" takes its rise; this Montefalco Mill Channel then feeds the industrial plant at Torre di Montefalco.

On the map the tag "Fiume Citunno" is mistakenly placed on Marroggia Creek; the Clitunno River is in fact the parallel channel immediately east of the tag that goes on to traverse Casco dell'Acqua.