The Boundary River is not like any river commonly seen by the world; in reality, it is a zone fractured by time and space.
In the Sea of Illusion's eye, the reason so many layered spaces appear is that they are sliced apart by various spatial turbulences. These turbulences eventually gather at what is known as the Boundary River.
In reality, every point where spaces connect is considered a 'tributary' of the Boundary River.
Such a Boundary River typically does not appear in stable time-space locations like Hongze; it only appears amidst the starry skies.
The Boundary River before us was drawn from the starry skies by a master of the Sea Tribe.
In other words, if one gets lost in the Boundary River, they might appear in the vast seas, possibly outside them, but most likely, they will return to... the starry skies with the river's backflow.
If someone's vision could break free from the shackles of time and space, they would clearly see a flat map.
