At first glance, this small living space on a Spanish sea-side cliff looks like a hollowed-out boulder with a window. Perhaps the most interesting part of the Truffle House is the unique process through which it was constructed, showcased in this video. To build it, the Ensamble Studio group began by digging a hole in the ground and pouring concrete into it. To create the hollow interior that would be the living space, they incorporated hay in the middle of the concrete. They then covered the whole structure with earth and let moss grow on it to give it an aged, natural look before uncovering it. The two ends were sliced off to create two openings and, finally, a cow named Paulina ate away the hay, opening up the space to fit a bed, kitchenette and sink.