What is the name of hell in Scandinavian mythology?

Niflheim is in Norse mythology, the cold, dark, misty world of the dead, ruled by the goddess Hel. In some accounts it was the last of nine worlds, a place into which evil men passed after reaching the region of death (Hel). Situated below one of the roots of the world tree, Yggdrasill, Niflheim contained a well, Hvergelmir, from which many rivers flowed.