This vast (150 kmē) and sparsely vegetated area on both sides of river Thjorsa (Bull's River) in the central highlands. Its southernmost boarder is river Hnifa, one of the western tributaries of river Thjorsa. The northern boundaries are the edge of the vegetated area. To the west and northwest the glacier Hofsjokull determines the western limits. On the eastern side of the Thjorsa river are two more vegetated areas, Eyvindarver and Thufuver, which belong to Thjorsarver. The greatest part of the area is wet and boggy and divided by many glacial rivers, tributaries of the main river, Thjorsa. It is the largest breeding colony of the pink footed goose in the world.

Approximately 6000 birds breed there every summer and about 20.000 leave and migrate late every summer, about three times more than migrate from any other breeding area, such as Eyjabakkar, further east. Both these areas have been earmarked for water reservoirs to supply hydro electric power stations and a part of the Thjorsarver area has already been flooded. This scheme has raised many questions and protests among those who want to preserve nature and the opposite reactions from those who support further industrialization.