Yggdrasill - the World Tree

Yggdrasill is an Ash tree, at the centre of all worlds. It is the World Tree of life and knowledge, and of time and space. On the highest branches sits an eagle, and twisted round its roots lies a snake, gnawing at the tree. The eagle and the snake hate each other. A squirrel runs up and down the tree, telling each in turn what rude things the other is saying!

Under the roots of the tree there is a spring of water called Mimir. If you drink from the spring, you will get wisdom and understanding. Odin thought it was so important to be wise that he gave one of his eyes for a drink from the spring. This made him the cleverest of the gods.