Rasiglia owes its importance to the Menotre River, fed by the major springs here present. The town is entirely built around the watercourse, formerly channeled for productive uses.
The Menotre river has a consistent and constant flow, despite having a not very wide riverbed. It flows for the first few miles squeezing through the narrow valley and has a luxuriant submerged aquatic vegetation. By its banks, grow hygrophilous riparian species predominantly of willows and cypress poplar.
Where the current slows down, small pools form and become the perfect habitat for the crayfish, a bioindicator species of the environmental quality as it thrives in fresh, clean and well oxygenated water.
Because of these unique natural features the Menotre River is among the Special Conservation Areas listed in the Natura 2000 network of Umbria.
