Reimagining design as a transformative practice for realizing a circular built environment is both urgent and important. Many of today's resource problems can be traced back to the way constructions are being designed. The adoption of circular design practices may alleviate these problems. Most previous research has either mapped the boundaries of contemporary circular design practices or pushed those boundaries with new interventions. The lived experiences of designers are, however, often overlooked. Little remains known about what it is like to be engaged in and how to ‘live through’ circular design. This study therefore seeks to understand the practice from the perspective of designers themselves. Through applying an interpretative phenomenological analysis to unstructured interview data collected from ten frontrunning Dutch designers, it explores both the what and how of circular design. Four emergent themes were found that illuminate the experience itself. Circular design is, accordingly, interpreted as a practice which: proclaims responsibility towards the Earth, materializes future-oriented solutions, deals with a multi-headed monster, and involves orchestrating a design ecosystem. These themes are illustrated with narrative accounts of designers' actual experiences. The rich, in-depth insights offer ample learning opportunities to better understand and facilitate unfolding circularity transitions. Circular design is, as such, theorized as a vital practice that can shape the built environment through materializing responsible futures.@en