This volume is dedicated to "Mechanics in Architecture", that is, the science of structural mechanics, including the behaviour of structures, internal forces, and deformation, as well as the development of new structural systems to resist thrusts as a result of new architectural forms. It is a field of enquiry that examines a particular aspect of the relationships between architecture and the mathematical sciences. Some of the papers in this issue were presented at the Nexus 2006 conference during a special session dedicated to mechanics. Other research papers focus on an eighteenth-century Belgian pyramid, aspects of "fractal" architecture, and properties of a family of irrational values. The issue also includes a description and evaluation of a university-level course in architecture and mathematics, Rachel Fletcher's Geometer's Angle column, and book reviews.