The Esper Saga
The Great Central Ocean
The Great Central Ocean is the ocean at the (supposed) center of the world. The actual center point of the world is Pandemonium, by design of the Espers, while the Great Central Ocean forms the center of the civilized human world.
The Great Central Ocean is nearly perfectly round, with a giant tower near the center – the Oubliette. Long ago, the Espers used this place to chain down their enemies, using the Ancients as guardians alongside Leviathan, whose Sanctum is nearby. The Great Central Ocean was frozen over by Sarasvati when she tried to kill both Leviathan and Shiva inside the Oubliette, but it has since begun thawing again.