Addressing the subject of Case-Based Design (CBD), the paper describes the development and use of a Web-based design tool called DYNAMO. The tool is firmly rooted in the Dynamic Memory Theory underlying the CBD approach. Yet, rather than adopting it as such, we have tried to enrich this approach by extrapolating it beyond the individual. This extrapolation stimulates and intensifies several modes of interaction. Doing so, DYNAMO tries to kill two birds with one stone. At short notice, it provides architects and architecture students with a rich source of inspiration, ideas and design knowledge for their present design task, as it is filled with a permanently growing collection of design cases that is accessible on-line. Its long-term objective is to initiate and nurture the life-long process of learning from (design) experience as suggested by the cognitive model underlying CBD, and Case-Based Reasoning in general. DYNAMO is therefore conceived as an (inter-)active workhouse rather than a passive warehouse: it is interactively developed by and actively develops the user's design knowledge. Whereas previous papers have focused on the theoretical ideas of DYNAMO, this paper points out how Web technology enables us to implement these ideas as a working prototype. Furthermore, an annotated scenario of the system in use is described.