The Tree of Yggdrasil
In the first film, Thor roughly sketched out how the nine realms fit together to explain to Jane how Earth relates to Asgard. In the sequel, we see how that’s integrated into Asgardian society via another important piece of Norse mythology in the tree of life.
Production Designer Charles Wood:
“That set’s all about the Yggdrasil, the tree of life. So what we’ve done is we’ve actually cast a real tree, so there’s an enormous tree which we’re gonna bring in here. And that’s the centerpiece of the set. And then when you walk in here and Natalie Portman is wandering around looking at the tree. That will all extend [Pointing Upwards] in visual effects. You’ll see all the nine realms floating within its branches.”