I remember yet the giants of yore
Who gave me bread; in the days gone by
Nine worlds I knew, the nine in the Tree
With mighty roots beneath the mold.
(Völuspa 2, translated by Ari Óðinssen)
This is the second verse from the Poetic Edda. “Nine worlds I knew, nine in the Tree”. The nine worlds come back in Northern mythology more often, such as in Alvíssmál 9 in which the dwarf Alvis says: “All the nine worlds I have travelled over” and also Vafthrudnir has travelled to nine worlds (VafÞrúðnismál 43). Because the concept is rather vague, it has been open to speculation what exactly these nine worlds are. Óðinssen writes in a note to the quoted verse: