Yggdrasil (from Old Norse Yggdrasill) is an immense mythical tree that plays a central role in Norse cosmology, where it connects the Nine Worlds.
Yggdrasil is attested in the Poetic Edda, compiled in the 13th century from earlier traditional sources, and the Prose Edda, written in the 13th century by Snorri Sturluson. In both sources, Yggdrasil is an immense ash tree that is center to the cosmos and considered very holy. The gods go to Yggdrasil daily to assemble at their things, traditional governing assemblies. The branches of Yggdrasil extend far into the heavens, and the tree is supported by three roots that extend far away into other locations; one to the well Urðarbrunnr in the heavens, one to the spring Hvergelmir, and another to the well Mímisbrunnr. Creatures live within Yggdrasil, including the dragon Níðhöggr, an unnamed eagle, and the stags Dáinn, Dvalinn, Duneyrr and Duraþrór.
https://en.wikipedia.org/wiki/Yggdrasil