Any space that involves descending from our typical aboveground environment is a provocation to our sensory perceptions. Such hidden spaces evoke latent mythical images and confront us with the clash between nature and artifice in our built environment. This book explores the character, use and design of underground space as a space of its own. International examples of commercial premises, restaurants, sports facilities, subway stations, museums, churches, libraries, concert halls, houses and other building types form the core material. Interviews with many renowned designers including Norman Foster, Floris Alkemade (OMA) and Francine Houben (Mecanoo) convey the architects' own views on the subject. Essays reflect on the cultural aspects, planning conditions, design considerations, technical requirements and sustainability aspects of building below ground level. Chapters include: Urban Development, Architecture, Functions, Perception and Cognition, Constructions, Energy and Interior Climate.