This introduction presents key concepts covered in the subsequent chapters of this book. The book analyses the structures of two contrasting buildings to set the scene for more focused and detailed explorations of many other buildings. Both buildings exemplify structure contributing architecturally in the context of specific architectural programmes. Structure is columnar, planar, or a combination of these which a designer can intentionally use to reinforce or realize ideas. In this context, columns, walls and beams can be thought of in terms of concepts of frequency, pattern, simplicity, regularity, randomness and complexity. As such, structure can be used to define space, create units, articulate circulation, suggest movement, or develop composition and modulations. In this way, it becomes inextricably linked to the very elements which create architecture, its quality and excitement. Roger H. Clark and Michael Pause's statement above begins by describing the architectural qualities of structure and then suggests how structure might enrich architecture.