without boost: torvus grove
When you enter the room from Underground Tunnel, go to the first tree on the left side. Jump on the grey object attached to the left side of this tree, then turn so you're looking at the tree. Walk forward until you stop moving, then jump backwards off of it. Near/at the peak of this jump, use your second jump and press against the tree until you land on an invisible ledge.
After you land, just turn around and space jump to the top of the room.