The pond reflecting a crescent moon.
The Pond is an area in the northeast quadrant of the Sketchbook in the game Ib. It is a blue pond drawn with crayon and contains dark blue fish. After Pandora's Box is opened, a crescent moon will appear in the pond when Ib stares at it. This is a clue to the puzzle in the Switch Room; the top-right switch will have to be pressed third, as the moon is third in the cycle.
If Ib dips her rose in the pond, it will lose one petal. If Ib feels the water, she will say that "the water's lukewarm." If Ib stares into the water before opening Pandora's Box, Garry will warn her not to fall in while she's spacing out. Ib can fill the bucket that she obtains from the small house in the Butterfly Park with water from the pond.