Saut du Day or Cascade du Day is a nice waterfall near Vallorbe and Ballaigues in the west of Switzerland (region Vaud).
From Vallorbe drive east to the train station “Day” over road 9. You can park your car at the train station (gps 46.717143, 6.400695). Walk a little back and take the tunnel that goes under the railway. At the main road go right and almost directly left. After the parking (not allowed for tourists) go right towards the river where Saut du Day (Cascade du Day) is located. A 10 minute walk.
Or you also drive a few hundred meters further passing the railway station, where there is a small parking (gps 46.715076, 6.405594) along the main road (at the left side). From the parking a path leads to the river l’Orbe. This is a little further but the trail looks very nice. Maybe a 15 minute walk?