 Later in "Gylfaginning", Just-as-High describes the central tree Yggdrasil.Just-as-High says that three roots of the tree support it and "extend very, very far" and that the third of these three roots extends over Niflheim.Beneath this root, says Just-as-High, is the spring Hvergelmir, and that the base of the root is gnawed on by the dragon Níðhöggr.