The Nupsstadur Forest is in the eastern slopes of Mt Eystrafjall, to the east of the edge of the vast glacier tongue Skeidararjokull and to the south of Lake Graenalon. Quite a few people, who drive up there, continue on foot to the lake or climb the sheer Mt Sulutindar nearby. The route between the main road and the forest is only passable by robust 4wd vehicles and their drivers have to be experienced in fording the rivers enroute. Sometimes their volume and current make such trips impossible. For those who undertake this adventurous journey, the surroundings and landscapes are unforgettable. In the wooded patch of land some wild sheep roamed about for several decades during the 19th century.
River Nupsvotn is the westernmost glacial river of the vast Skeidararsandur Area. It gets its name after the confluence of Rivers Nupsa and Sula directly under the bridge. River Nupsa is a spring fed river and River Sula, which is much larger glacial river. Dykes were built to restrain them before the construction of the bridge was begun. All four bridges on the alluvial plain were officially opened in 1974, when the Icelanders celebrated the 1100th anniversary of the inhabitancy of the country.
During the first half of the 20th century the “glacier bursts” (regular floodings) were very large and peaked at 5-10 thousand m³/sec., when the Lake Graenalon was emptied after having become 150-200 m deep. Nowadays the glacier bursts are less regular and peak at about 2000 m³/sec.