The middle-world of Midgard, where people dwell, has also other residents: the dwarves
of Nidavellir and the giants in
Jotunheim. It was shaped from the eyebrows of the great
frost giant Ymir, after he had been slain by the Allfather and his brothers, Vili and
An indestructible rainbow bridge called Bifrost leads from this land to Asgard above it, and these two and Niflheim below all lie beneath the branches of Yggdrasil, the World-Tree, which is eternal. The Spring of Mimir lies where its roots find Midgard, guarded by the head of Mimir himself. This head, severed by the Vanir when they found their hostages unsatisfactory, was kept alive by the magic of Odin, who gave one eye to drink from this spring and often sought his fallen companion's advice there.