Along the edge of the Sagouri Swamp and the Great Marsh, set partially around sunken into a slow moving river, sits a massive edifice piercing upwards from the soft ground below up to the canopy above. It appears that the building sinks deep into the ground below, partially by intent - the river, which must have once have been powerful, is fed partially into the facility itself, but also from the ages that have softened the ground beneath causing it to sink awkwardly underground leaving it arched upward at a roughly 45 degree angle. At its proper height and orientation it looks like it may have even straddled the river entirely, forcing it to flow within before exiting towards open water.
The writings and runes mark it as a "recent" complex relative to the many ruins you have seen, younger than The Bastion
and The Academy Ruins
. Despite this it is hard to ascertain the intent of the facility, though your time in the Time Loop marked it as a "Naval Base."
The Great Marsh rises up along the northeastern edge of the facility, a vast green sea of serpents and other strange horrors, with its western border marked by the slowly moving river that leads north towards the distant mountains of The Bone Hills
Purpose / Function
From the Time Loop you learned this was a "Naval Facility" which apparently housed some of "Magi Montsavari's Works"
The building has sunk into the marsh and is now perched at a 45 degree angle up above the western edge of the river which partially filters into the facility.