Alftafjordur is a lagoon that Starmyrarfjordur, which is no wider than a large surf crosses them, separates the lagoon from the sea. The fjord is quite large, but relatively shallow and large areas of it dry up when the tides are low. There are several islands in Alftafjordur,
To the south of the fjord rises Krossanesfjall, just over 700 m high straight up from the sea, but to the north are Maelifell and Sellond. When this is released, we receive four valleys that rise from Alftafjordur, to the west. Their southernmost is Starmýrardalur. The mouth of the valley is narrow, but when it enters it opens slightly but high mountains, Flotufjoll and Midfell to the south and Selfjall to the north, rise rapidly. Selá lies around the valley and has its source at the top of Starmýrardalur. At the mouth of the valley, the river flows through Sjónarhraun and from there in a bend to the northwest over Stekkjartun where it joins Starmyrara, which originates in Hædir. From there, Sela falls into Krossavik south of Alftafjordur.
The mouth of Flugustaðadalur is to the south of the rivers and the mouth of Hofsdalur to the north, the division remains so until Tungutindur takes over and separates the valleys, so that Flugustaðadalur stretches further west and Hofsdalur bends to the northwest. Both valleys are fairly well-vegetated and there is considerable birch scrub. When you reach the valley, you face Jokulsgilsgrindur, Grisatungur and Hofsjokull (1280 m).
At the northern side of Hofsdalur, steep mountain slopes take over and Selfjall (950 m) is the highest peak and beyond the mountain range is Geithelladalur, about 18 km long. High mountains are bends due to the valley all the way west of Þrandarjokull (1248 m) on the south side, but when you reach the bottom of the valley, land rises rapidly and the plateau northeast of Vatnajökull, so-called Hraun, is exposed. The valley is grassy and there is a lot of forest there. The Geithellaá river flows through the valley, which is a considerable waterfall and has its main source in large water into lava. It falls through Geithelladalur in waterfalls and gorges until it reaches the lowlands. From there it flows through gravel ears and falls into branches to the west of Alftafjordur.