In Norse mythology the Nine Worlds connected by the world tree, Yggdrasil, were broken into three levels.

• At the top level were Asgard, the home of the Aesir; Vanaheim, the home of the Vanir; and Alfheim, the home of the light-elves.
• At the middle level, and connected to Asgard by Bilrost, the Rainbow Bridge, were Midgard (Middle Earth), the home of humans; Jotunheim, the home of the Jotun, or giants; Nidavellir, the home of the dwarves; and Svartalfheim, the home of the dark-elves.
• At the bottom level, the underworld, were Niflheim, world of the dead, cold, and misty, whose citadel was Hel, home of Hel, queen of the dead; and Muspellheim, world of fire, presided over by the fire god, Surt.