The Stone Demonstrator is a research pavilion developed through Future Observatory at the Design Museum to explore the potential of natural stone as a low-carbon structural material. Designed by architect Groupwork with structural engineers Webb Yates and Arup, the project investigates how pre-tensioned stone can provide a low-carbon alternative to conventional steel and concrete construction. The pavilion uses locally sourced stone blocks assembled through dry-stacking, removing the need for mortar or mechanical fixings and creating a structure designed for future disassembly and reuse. The project draws on traditional masonry techniques while applying contemporary structural analysis to demonstrate how stone can be reconsidered within circular construction systems. By using a durable, abundant and minimally processed material, the demonstrator investigates opportunities to reduce embodied carbon through material longevity, reversibility and simplified construction. The pavilion forms part of ongoing research into regenerative approaches to architecture, where material selection, structural logic and end-of-life considerations are integrated from the earliest stages of design.