Yggdrasill
The World Tree Yggdrasill is a semi-real cosmological concept in Asgardian religion and cosmology. It connects the Nine Realms and allows passage between them. Although the Nine Realms all occupy specific points on the tree, its magical and unreal nature means that parts of the tree can be accessed in places which do not make logical geographic sense, e.g. a pool formed in Yggdrassil's roots is accessible from the British Isles, even though Midgard is located in the tree's branches.
Communing with or sacrificing too the tree can grant a variety of magical abilities, including the ability to see the future or past, or knowledge of magic (such as was granted to Odin).