Where does the river " janus "

A border of Umbria and the Marche region created a cute and pristine river from the ancient name of Janus.

In Roman mythology, Janus (or Ianus) was the god of gates, doors, doorways, beginnings and endings. His most prominent remnant in modern culture is his namesake, the month of January, which begins the new year. He is most often depicted as having two faces or heads, facing in opposite directions.