The Hachimantai Dragon Eye appears when the snow around Kagami-numa melts before the centre of the pond, leaving a blue-and-white ring that looks uncannily like an eye. It is a natural effect, not a fixed attraction, and the famous window is usually only from late May into early June.
The pond is near the Hachimantai mountaintop promenade. Expect snow or mud underfoot during the viewing season, and do not build a whole trip around seeing the eye in perfect form; the walk and the highland scenery still make the detour worthwhile.