Valley Bardardalur stretches far into the interior between Moorland Fljotsheidi in the east, Valley Fnjoskadalur in the west and Valley Adaldalur in the north. The southern boundaries are at the beginning of the interior Sprengistandur Area and the western edge of the Odadahraun Lava Field. It is among the longest inhabited valleys of the country (35 km between the southernmost and northernmost farms). It is rather narrow between the steep and well vegetated slopes on both sides. The valley floor is a flat branch of the Odadahraun Lava Field, vegetated with i.e. willow, heather, dwarf birch and meadows. Remnant woodlands still decorate the western slopes, and many areas are well suited for cultivation.
The valley most probably was created by subsidence. The structure of the mountains on its western side (600-700 m) is basalt, but hyaloclastites on the easter side (200-300 m). The 175 km long River Skjalfandafljot, with its southernmost catchment area in Pass Vonarskard, runs through the valley. At the southernmost end of the valley, the beautiful Aldeyjarfoss Waterfall cascades into a gorge framed with basaltic columns, and at the northern end Waterfall Godafoss decorates the landscape.
The first Norwegian settler of the valley was Bardur Heyangurs-Bjarnason, who built his farm at Lundarbrekka, but later on moved across the interior to the farm Nupar in the Fljotshverfi district.