Strange Cave Found In The Cotl

Today I discovered a strange cave in the Canyon of the Lost. It doesn't seem to be accesible by any path, instead you have to go over a small wall to get there, and I don't think this belongs to any quest because of this.

Spoiler: The first room

The first room of the cave is pretty bland, it's just a small room with a loot chest and a path downwards.

Spoiler: The second room

The second room is, at first glance, just a small subterranean lake with a path above it. There is however, a button hidden underneath the path.

Spoiler: The third room

The third and final room of the cave contains some kind of collapsed structure with what seems to be a grave inside it.
As far as I know, the button does nothing. The place also is mentioned nowhere on the wiki. So does anyone else know what this cave is for, or what the button does?

The coordinates for the cave are 650, 54, -4830 if you want to explore it yourself.

 

i haven't seen this before nice find

 

have found this before, and I couldn't figure out what the button did either :/

 

Explored this with a friend WAY back, and we confirmed that the button does nothing.