The waterfall of the “Gueule de l’enfer” = Mouth of Hell is fed by the brook Merdaric in the town of Thueyts. It is ephemeral and is visible only during heavy rains. You can observe it along the hiking trail that leads to Devil’s Bridge.
It can sometimes be very impressive in certain seasons with a vertiginous jump of 80 m of water from the top of the basaltic flow of the Giants Causeway.
All year round.