Altostrata is a 30-metre-long, 3D-printed travelling auditorium made from compostable sugar-based PLA bioplastic. Designed by Mamou-Mani Architects and produced with Fab.Pub’s mobile 3D printing factory, the modular structure comprises 12 bespoke components reaching 2.7 metres high. Parametrically optimised as a space truss, each piece can be hand-assembled on site. Printed in just three weeks using a single robotic arm, Altostrata demonstrates the structural potential of bioplastics, achieving resistance to 500 kg/m² pull forces. First installed in Romania, then Singapore and Dubai, it embodies circular design through its modularity, compostability, and reuse potential, pushing the limits of sustainable architecture.