Eden Project, Cornwall, UK, designed by Grimshaw Architects and completed 2001. Produced by Vector Foiltec, each bubble consists of layers of ethylene tetrafluoroethylene (ETFE), welded around the perimeter to trap a layer of insulating air within. ETFE was selected for the transparent envelope, because it enabled an extremely lightweight and efficient structure. The film allows a high level of light transmission, is extremely resistant to UV and weathering, self-cleaning due to its low surface energy, and can tolerate abrasion from grit in the wind. Image Vector Foiltec.