Heiðrún
In most portraits that show the goat, she is shown as a very large creature standing on top of the roofs of Valhalla. She is seen in a way similar to Ratatoskr, the gossip loving squirrel that tends the world tree. Because of this, some historians think that Heidrun would eat the leaves from the upper branchs of Yggdrasil that are pushed to Valhalla. This may mean that Asgard is also up there. The Norse were very vague about where they thought the realms were on the tree.