This book presents the catalog of a virtual exhibition featuring the structural visualizations of 93 Web APIs of different sizes and shapes. The diagrams are drawn based on the exact API specification found on some open source repository. While there are many books on how to design good APIs, the goal of this book is to show a small sample of actual API designs. There is a lot that can be learned from them. All APIs represented are Web APIs: they come from the time when many attempted with very different results to use the HTTP protocol to remotely invoke software delivered as a service. The APIs have been selected mainly due to their visual appearance.