Yggdrasill
A cosmic ash tree, Yggdrasill, lies at the center of the Norse cosmos. Three roots drink the waters of the homeworlds, one in the homeworld of the gods, the Æsir, one in the homeworld of the giants, the Jǫtnar, and one in the homeworld of the dead. Beneath the root in the world of the frost giants is the spring of Mimir, whose waters contain wisdom and understanding.
The root in the Æsir homeworld taps the sacred wellspring of fate, the Well of Urðr. The tree is tended by the Norns, who live near it. Each day, they water it with pure water and whiten it with clay from the spring to preserve it. The water falls down to the earth as dew.
Animals continually feed on the tree, threatening it, but its vitality persists evergreen as it heals and nourishes the vibrant aggression of life. On the topmost branch of the tree sits an eagle . The beating of its wings cause the winds in the world of men. At the root of the tree lies a great dragon, Niðhǫggr, gnawing together with unnamed serpent at it continuously. The squirrel Ratatoskr carries insults from one to the other. Harts and goats devour the branches and tender shoots.
Read more about this topic: Norse Cosmology