Callanish I was constructed around 3000 BC from huge monoliths of Lewisian gneiss showing veins of quartz and other crystalline minerals. The age of the rock is truly staggering, it is though to be nearly 3000 million years old, making it some of the oldest geology in the world. At dawn a brief flash of sunlight revealed a striking image, moments before the grey mass of stratus cloud swallowed up the sun for the remainder of the day.