In the distant waters of the South Sea, surrounding the Nameless Reefs near the Odell Reef Cluster.
A world completely enveloped by water.
This place was a secret ocean blue hole in the center of the reef cluster, featuring a suddenly plunging dark sea area, brimming with seawater, yet possessing a hidden drainage pipe deep within the cave entrance.
Every so often, the water inside the blue hole would drain completely, until rising tides brought about by the ebb and flow of the sea tides filled it once more.
The entrance to Redwood Base was located at the top of a 'Z-shaped' hole at the bottom of the blue hole, where a peculiar air wall separated the seawater; arguably, the drainage at the bottom of the blue hole likely led straight to the cooling area – in other words, a hidden entrance that could never be filled, yet was always blocked by deep sea waters.
Of course, to the pre-era civilization, this was probably just an exotic landscape.
