A quick walk through the forest near Biei, Japan, leads to a mesmerizing scene straight out of a fairytale. There, a brilliant blue pond lies tucked away within the woods. Dead silver birch trees poke above the water’s edge, their reflections seemingly painted on a glassy canvas.

The artificial pond was created in 1988 when the Biei River was dammed to prevent damage from mudflows from the eruption of nearby Mount Tokachi. What was supposed to be just an effect of an environmental engineering project created a breathtakingly beautiful human-made wonder.

The pond’s cerulean hue is thought to be caused by aluminum hydroxide suspended in the water. Aluminium hydroxide reflects shorter-wavelength blue light, meaning that the water itself isn’t actually blue. But that doesn’t make it any less captivating.

The enchanting color changes depending on the angle from which you view it, the time of day, and the season. When the air is still, it reflects the trees submerged within their watery grave like a blue-tinted mirror. Though the pond freezes over during the colder months, there’s now an annual tradition of illuminating the water each season, creating an ethereal glow beneath the blanket of snow and ice.

If the pond looks at all familiar, there’s a good reason why. It gained international recognition after Apple included an image of it as a wallpaper in OS X Mountain Lion, which was released in 2012.