Fremri-fellsfoss is a 15-meter high and quite majestic waterfall located on the lower course of the Skógá River along the Fimmvörðuháls trail. It is a 2.2-kilometer hike from the Skógafoss waterfall parking lot, with an elevation gain of 195 meters.
The other waterfall you see in the background from here is Innri-fellsfoss.
