Moshe Safdie invented Habitat 67 in Montreal, Canada as part of Expo 67, one of the world's largest world expositions, which focused on themes of housing and shelter. Habitat 67 consists of 354 interconnected prefabricated concrete housing units stacked in an innovative design, providing 146 residences between sky and earth. It took extensive planning, including over 4,000 drawings and models, to design and build Habitat 67 at a cost similar to constructing traditional townhouses.