Hard to say. The setting is easy to recognize, it's the reservoir in the town of Baron. There is a dancer up there, who does a short routine. But then, the hairdo is rather Rosa-ish, and the sprite used for the dancer has red hair, on the SNES at least.
I commissioned it back in 2006 (as her watermark shows on the bottom left). I can't remember if I based the dancer idea on a story I wrote or if that came after the art, but whichever way, I liked the idea of Rosa as one of the dancers. I did have one story by then with a scene of her back there, but I wrote another too at one point.