This is the second largest spring fed river of the country. Its sources are numerous cold springs beyond the pass Bruarskord in the mountains. Its name is derived from a former natural stone arch across it. One of the bishops' wives at Skalholt had her chef demolish it to prevent vagrants from frequenting the seat of the bishops.

The river is about 38 km long and tributes to the glacial river Hvita. The best fishing spots are 4-5 km to the north of and 2,5 km to the south of the bridge across it north of Skalholt. There are excellent fishing spots in that area and the catch is Sea Char, Sea Trout and the occasional Salmon. The river is excellent for experienced anglers.

The distance from the capital is about 85 km.