Along the CAI path no. 420, near the aqueduct building, a detour to the left leads to the source of the Fontanon di Timau, a Geosite of regional importance. This is a powerful perennial karst spring and has been known since Roman times. Today its waters are used to generate hydroelectricity and, in part, for the mains supply. The maximum flow rate may exceed 5,000 litres per second and the waters that feed the source also come from the limestones of Monte Coglians. The water flows from several mouths that open in the rocky wall at the base of the Creta di Timau before forming a short but steep stream that flows over the boulders of the morainic deposits that are partially cemented together by travertine deposits.