Gullfoss is actually two separate waterfalls, the upper one has a drop of 11 metres and the lower one 21 metres. The rock of the river bed was formed during an interglacial period.
Water flows over Gullfoss at an average rate of 109 cubic metres per second. The heaviest floods have recorded a flow of 2000 cubic metres per second. During the summer the flow is 130 cubic metres per second, which would take only 3 seconds to fill this building. People were eager to exploit the power potential of Gullfoss and many plans for hydroelectric developments on the river Hvítá have been proposed.