What hidden geometry links Gothic cathedrals, Moorish palaces and Mughal domes? How do you draw a four-centred arch? Why do arches feel so uplifting? How many different kinds of arch are there? In this delightful pocket book, architect and geometer Jon Allen shows us how to set out arches, from simple semicircles and pointed lancets, to Tudor gateways and Islamic masterpieces. An inspiring guide for architects, artists, designers, builders and all lovers of beauty and sacred geometry.