Lake Isholsvatn has an area of 5,2 kmē. It is 5 km long, 39 m deep and is situated a short distance south of the farmstead Myri in Valley Bardardalur in the North.

River Langa and other brooks spill into it and river Fiska is its discharge. Close to the lake is a beautiful waterfall Aldeyjarfoss in the river Skjalfandafljot, framed with natural basaltic columns. The catch consists of brown trout and lake char, both large and small.

The distance from the capital is 458 km by the Whale Bay tunnel and 358 km by the highland road Sprengisandur.

Aldeyjarfoss 15 km <Isholsvatn> Kidagil 20 km.