Glymur, with a cascade of 198 m, is the second-highest waterfall in Iceland. It was long regarded as the tallest waterfall in Iceland until being surpassed by a newly measured waterfall near Morsárjökull in 2011: Morsárfoss.
It is situated at the rear end of the Hvalfjörður. Since the opening of the tunnel under this fjord, most people bypass the area. However, it is a very beautiful part of the Hvalfjörður with some tall mountains and forests.
The river Botnsá runs from the Hvalvatn lake and after a short distance the water falls down alongside the Hvalfell mountain into a steep canyon. The waterfall can be accessed from a parking area at the end of the road. Well-equipped hikers can view the waterfall from marked paths on the east side of the river Botnsá.
Source: https://en.wikipedia.org/wiki/Glymur