Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. Valhalla is the largest multi-ring structure (impact crater) on Jupiter''s moon Callisto and in the Solar System. It was named after Valhalla, Odin''s hall in Norse mythology. Valhalla consists of a bright central region 360 km across, an inner ridge and trough zone and striking concentric rings extending up to about 1,900 km from the center. Several large impact craters and catenae are superimposed on Valhalla. Valhalla multi-ring system is of impact origin and may have formed as semi-liquid or liquid material underlying the brittle lithosphere punctured by the impactor slumped towards the center of the crater following the impact.