 This specific meaning for "lower plain" derive from a geologic feature called the "fontanili" ("spring") line or zone, a band of springs around the Val Po, heaviest on the north, on the lowermost slopes of the anticline.It varies from a few kilometres to as much as wide.The fontanili line is the outcrop, or intersection, of the anticline's water table with the surface at the edge of the "bassa".