Halleberg
Halleberg is a table mountain by lake Vänern in Vänersborg Municipality, Västergötland, Sweden. Halleberg, part of which protrudes into Lake Vänern is separated in the south by about wide valley from the adjacent Hunneberg (also a table mountain). The northern part of Halleberg called "Hallesnipen". Geology. Hallberg has an average height of about above lake Vänern, or above sea level; the highest point is above sea level. Halleberg consists of Cambrian, Ordovician and Permian rocks. The Palaeozoic rocks are deposited directly on the crystalline peneplain bedrock, which in this range consists of göta granite. The Cambrian sedimentary rocks are  sandstone and alum shale. The sandstone layer is on average thick. Above this there is then a thick slate which in turn covered by about of alum shale. The Ordovician is represented by a calcareous slate. During the Permian it was pushed into diabase which lays as a protective cover and thus protect the mountain from erosion. The diabase on Västgötabergen known locally for staircases. Economic Geology. Anthraconite, alum shale and diabase has previously been mined in several places on the mountain. Nature. Around the food of the Halleberg are elongated scree of large stacked, sharp-edged boulders. In a  few places, there are so-called steps, where there are roads or paths up the mountain. The vegetation on the mountain plateau is dominated by spruce and pine, and the expanse of bog, while on scree lower parts are more species. In contrast to Hunneberg, on Halleberg there is simply lake "Hallsjön", three-kilometer long but narrow. On Halleberg is the Ecopark Halle-Hunneberg (comprising the Halle- och Hunnebergs platåers naturreservat and the Halle- och Hunnebergs branters naturreservat). Halleberg Ancient Fortress. Halleberg is also Scandinavia's largest hillfort (about ). It is almost completely naturally fortified by the mountain's steep  slopes, large stone ramparts being primarily at the "Storgårdsklev" steps in the southwest. There are three stone ramparts, with a total length of , of which the longest is about long and high. Small ramparts have in passable gaps, for example at the "Lilleskog and Björkås trappa" staircase. The hill fort was built during the Migration Period of the 3rd-4th centuries. It was a refuge during the Swedish-Danish wars of the 15th-17th centuries, for example during the Gyldenløve War in 1676, but also during Gustav III's Russian War of 1788. The Danes only managed to conquer the castle once , in 1612. During the Basse War ("Bassefejden" in Swedish) of 1490–1510, Halleberg was besieged for seven years. The place name (in about 1325 "Haal"), had previously only a hall, including a 'rock face' entrance hall, a 'cliff' or similar. Halleberg in mythology. Halleberg is considered by some to be the location of Valhalla. Part of the mountain is still called "Häcklan". One of Odin's name was "Häcklaman".