3D printer-hackers at McGill University in Montreal have modded their 3D rig to print solids made from ice. Scaled up, they believe they'll be able to create large-scale ice buildings, but for now, they're using it for very temporary, very cold, very intricate rapid prototyping:
Currently, the practical applications of this project include commercial and industrial part modeling, and construction for the ice-tourism industry. For instance, small-scale ice models represent economical alternatives to intricate 3D models of architectural objects, be they scale models of buildings, site models, or building details. Presently, casting techniques are being investigated in order to produce high-quality metal copies from ice originals. In the long term, inhabitable, environmentally-friendly structures will be built at the architectural scale using computer-assisted techniques, thus increasing the level of automation in an industry that is currently very labour intensive.