There's actually nothing there.
These areas are absolutely empty. There are some of the hair-like doodads from the starting area, but nothing else notable or hidden around the edges of the map. I spent way too much time mapping this all out and collecting screenshots, but it's literally just empty space.

I assume this is an intentional development decision because the game is supposed to pressure you for time, you're not supposed to be rewarded for going wildly off track.