In Norse mythology, there were nine worlds all connected by the world tree Yggdrasil. The enormous ash tree connected:
- Asgard, the home of the Aesir, one of the races of gods
- Alfheim, the home of the light elves, the domain of Freyr
- Vanaheim, the original home of the Vanir, the other race of gods
- Niflheim, the world of darkness, from whence eleven ice-cold rivers flowed
- Midgard, the home of mankind
- Muspelheim, the home of the fire giants
- Jotunheim, the frozen, mountainous home of the race of giants called Jotun
- Svartalfheim, the home of the dark elves
- Hel, the underworld where the death goddess Hel resides