Once upon a time the ancient palace at Knossos on the island of Crete was made of smooth white blocks of gypsum with polished surfaces that gleamed in the sunlight. The effect of weathering over the centuries has stripped away the surface of the building blocks and created rough textures and patterns of sharp edged furrows where acid rain has dissolved the stone as it runs over and down the masonry. The gypsum blocks mimic a phenomenon called rillenkarren found on a larger scale in limestone landscapes all over the world. These erosion patterns in the landscape are known as karst topography. I previously photographed an example of karst topography with rillenkarren in the Queensland outback in Australia near the old mining town of Chillagoe.