Gljúfurárfoss is easy to overlook even though it is situated only a couple of hundred metres from Seljalandsfoss. It is sometimes referred to as “the secret waterfall”, as it is partly hidden behind an outcropping of rock and can only be seen in full if you are standing in the middle of the river, or, if the water-level is low and you can get inside, in the grotto between the two cliffs where the fall comes down.
On the bright, sunny day I was there one would have needed HDR trickery to get a good photo of the falls but I did not want to risk getting my camera wet while fiddling with a tripod and just did a quick in-and-out to snap some shots. This was my best effort of the fall itself:
This photo has the waterfall overlit but shows the moss-covered rock walls of the cleft in the rock one passes through to approach the waterfall.