GO is a peaceful area full of greenery and flowers. This is the location of the final boss battle with the Briar. One can receive the Swap here, which is necessary to reach the location of the final boss battle.
See Color Puzzle.
After completing the NPC Quest, the stairs in the northeast corner of the main courtyard area become active. Once you enter New Game+, you can use the Swap to access the stairs. The stairs lead to the Secret Room.
The Secret Room has blinding light and a rock which says:
The shiny rock reflects only a bit of the light from the room. There is writing etched into it: "Quickly, before I have to leave again (It is getting very light in here, this always happens) - the northwest part of the blue forest - I saw another temple entrance just to the north, past those trees - if only I could switch things at will to get through there...maybe I'll do this the next time I revisit this world."
The rock can also say:
You actually were...uh, ah. Well done.
The rock gives a clue about the location and existence of Overworld Station.
This room cannot be accessed using the Swap, but can be accessed using the Wiggle Glitch to bypass the NPC Quest. (The Swap will not work, because the water channels contain BG2 wall physics tiles, and the "default tile" in GO has wall physics. You can almost get there using PU-1, but there is still 1 wall tile in the way through that route.)
WARNING: Once you've entered the secret room and seen the bright lights, every screen in GO will contain the bright lights effect. Leaving and reentering GO will not fix this. This glitch will persist until either you close the game, or simply go to the title screen. It is harmless to save while this glitch is active; it does not get stored in your save file.
Second Color PuzzleEdit
See Secret 10.
Trashed Color PuzzleEdit
This screen is what looks like a color puzzle that has been trashed with the Swap. This screen appears to serve no purpose in the game.
Empty Boss RoomEdit
You can access the boss room used during the Briar fight by swapping through PU+1, although it's very difficult. An easier way to reach it would be using the Wiggle Glitch. Accessing this room without beginning the boss fight the intended way serves no purpose.