If they wanted to keep it hidden, then why did Zee let us in here? Maybe half the reason they haven't been able to tell us any of this stuff is because it's been lost in this mess.

[let's be real, you could lose pretty much anything in this room without even trying]

Now that you mention it... there's tunnels on this map that weren't there the previous times I went down. Like... here... and here. I should have passed those tunnels. But they definitely weren't there.