Well actually, maybe I have made a discovery! That place is the garden right? With the Y glyph with 1 superintendent face? Well, the very first times I played the game when I went there, there was always a tri glyph, slightly below where the glyph is now. The glyph thats there now wasn't there.
Thats why i put it there, but if it was only me who saw it i may as well take it down.