Yggdrasil

The main thing limiting vision is the fact it's a tree, with lots of branches and leaves that are getting in the way.

Arlen does understand the gravity correctly, and goes on his looping run down the branch. The main trunk is many miles thick; thin enough that it doesn't fill the eye like a continent, thick enough that it's a serious amount of tree. After they're all through, the sprouting branch from which the portal opened splits and morphs back into a dryad- Veggmaleri is here, too.

Anybody looking closely enough may note, far in the distance in what might be 'up' the tree (it's hard to tell), a cluster of regular shapes built about the base of a larger branch.