Even if you can’t pronounce it, you have likely heard of the great World Tree called Yggdrasil. It’s part of Norse mythology, and is literally the central part as this ash tree is believed to grow up through of all the various worlds, connecting them.
I’ve always envisioned this tree with its roots in the underworld (Niflheim) and its highest branches in the realm of the Gods (Asgard). Well, that’s not really how it’s laid out after all. There are 3 roots to Yggdrasil, and under each of the roots is one of the mythological worlds: Asgard, Niflheim (or Hel), and Jotenheim. The trunk of the tree runs through the realm of man, Midgard.
The tree is not simply a supporting structure for these worlds, there are other landmarks and inhabitants as well. Under each of the roots, is a sacred well, one of which is tended to by the Norns. These 3 women control time and destiny by weaving threads, much like the 3 Fates of Greek myth. They also water the roots of Yggdrasil with the water from that well.
There are also several animals that live in Yggdrasil. A bird (a rooster or an eagle) living among the branches, a dragon that chews the roots, and a squirrel that runs up and down the trunk with messages between them. Four deer or stags are also living in the branches of the great tree, representing the 4 directions.
At Ragnarok, Surtr (leader of the fire giants) will set fire to the tree and bring about the end of the world. Two humans, Lif and Lifthrasir, will survive the destruction by hiding among the branches of Yggdrasil and will repopulate the world after this great battle of the Gods.
A few more details. Yggdrasil is pronounced “IGG-drah-sill”, according to some Asatru message boards, and the name is translated to mean “terrible steed”, though sometimes also called Odin’s steed or Odin’s horse. The tree is associated with Odin because the God hung from the branches for 9 days in order to learn the mysteries of the runes.