The modern world is dominated by flat surfaces. We write, print and project on flat paper or flat screens, which we stare at all day. We inhabit spaces constructed from flat materials. We play sport on level fields. Engineered planar surfaces have become so pervasive and fundamental to behaviour and thought that we barely notice their existence. But flat landscapes are also often disparaged, viewed as featureless, empty and monotonous. Metaphorically, to ‘feel flat’ is to be bored, dull, lacking energy or inspiration. So what is it about flatness that makes it so desirable and practical in everyday life, yet so unattractive in landscape and as an idea? How has the construction of flat surfaces contributed to a degradation of visual diversity? Flatness attacks these questions by looking first at the ways humans have perceived the natural world around them, from Flat Earth theories to abstract geometric concepts and the Flatness Problem in modern cosmology. It also traces the long