American Onsen is a book that guides the reader to learn how to take the ancient art of mineral spring bathing and redevelop it into a spa structure that can be enjoyed by any Western consumer. By looking at the Japanese mineral spring bathhouse design parameters and exploring the social, physiological/ psychological, medicinal and spiritual benefits of the mineral spring bathhouse spa in detail, designers and spa owners can learn how to create an environment that harmonizes mind, body and soul through its interior design. The Japanese have perfected the art of designing these environments for centuries. This book explores how we can build upon their knowledge of this specialized type of spa experience, and successfully adapt this art to western cultures, taking into account anatomical and cultural differences as well as the importance of biophilia, materiality and lighting design.