When Coleridge described the landscapes he passed through while scrambling among the fells, mountains, and valleys of Britain, he did something unprecedented in Romantic writing: to capture what emerged before his eyes, he enlisted a geometric idiom. Immersed in a culture still beholden to Euclid's Elements and schooled by those who subscribed to its principles, he valued geometry both for its pragmatic function and for its role as a conduit to abstract thought. Indeed, his geometric training would often structure his observations on religion, aesthetics, politics, and philosophy. For Coleridge, however, this perspective never competed with his sensitivity to the organic nature of his surroundings but, rather, intermingled with it. Situating Coleridge's remarkable ways of seeing within the history and teaching of mathematics and alongside the eighteenth century's budding interest in non-Euclidean geometry, Ann Colley illuminates the richness of the culture of walking and the surprising potential of landscape writing.