The Aiso Spring or Aiso Lake, with its 0.27 hectares, is the smallest of the Natura 2000 sites in Umbria. It is a small lake located between the Topino and Timia rivers, generated by a spring and characterized by a considerable depth and almost vertical walls. The most salient aspect, from a geobotanical point of view, is given by the presence of algae and vascular hydrophytic species.
The lake was a worship site since pre-Roman times. It is the protagonist of the legend of a farmer who wanted to thresh on July 26, during the feast of Sant'Anna: the wicked gesture was punished by the sinking of the farmer into the abyss, in the place where the lake was born. Not far away, archaeological excavations have revealed the traces of a Roman sanctuary with a spring water collection tank.
The Aiso Lake is inserted in an agricultural context with intensive cultivation: the use of pesticides, herbicides and fertilizers represents the most important threat to the conservation of the biodiversity that characterizes it.
