Everyone else has made the points I wanted to make. A potentially great game, but figuring out exactly how things are supposed to link up is kind of frustrating.
It was right next to the bottom-left mirror. If I remember right, the flame was sort of balancing on the edge of the mirror. That one glitch aside, I really like this game.
For some reason, I can't use any items in the underground part. I was able to do it before, but once I finally collected the right items, it stopped working. Great game, though!