Recent literature in geographical and environmental studies, and environmental aesthetics, has focused on the concepts of the post-industrial city, urban nature, and urban ecological citizenship, in an effort to develop new approaches to the design of the sustainable city. This paper will explore the role of heritage through the concept of “deep cities,” defined as “a city’s long-term history and heritage.” I will argue that the planning initiatives of the early 1960s in the urban theory of Van Ginkel Associates, Montreal, fit this definition through the importance that the planners placed on heritage within Montreal’s urban development. The desire for conservation of the Old City of Montreal in this case was an active force that was essential to changes that prevented the loss of the greater cultural environment, which included the industrial landscape of the Port and the Lachine Canal. As the planners suggested, the city is a fabric in which any change in one part causes inevitable change in another. However, in addition, the urban landscape is more than the reflection of modes of production; it has a logic and structure that both resists and drives change. I will use as a case study the preserving of the industrial environment of the Lachine Canal in conjunction with the perceived heritage value of Old Montreal as representative of an ecology of place, which offered a plan for urban sustainability. Within this process regarding the sustainability of the industrial landscape, the planners took the initial steps toward saving the Old City at a time when preservation of the old quarter was of little interest; Van Ginkel Associates advocated restoration and preservation for the Old City in an attempt to create a densely populated area, and to restore Old Montreal to a working part of the city. The firm fought a proposal for an East-West Expressway that would unload a tremendous volume of traffic into the Old City and thus destroy it; would erect a barrier between the harbour and the city; and would adversely affect the valuable industrial area along the Lachine Canal. With the opening of the St. Lawrence Seaway, the Canal was no longer the main gateway to the Great Lakes, and its use was left in question. Two suggestions had been proposed by the City of Montreal: the closing and filling in of the Lachine Canal, and the closing of one end of the Canal. The planners insisted that both of these proposals were irresponsible and developed a series of arguments for the continued use of the waterway suggesting that it was an economically viable part of the city. Due to the instability of its future, for the previous seven or eight years, the area had attracted no new industry. The planners recommended that the Canal be considered a shipping basin, a service waterway for industry. Furthermore, they recommended that the Canal remain open for the use of pleasure craft. The planners drew on experience in postwar Amsterdam in the rehabilitation and reconditioning of buildings for new industry. They suggested that old buildings suitable for conversion along the Lachine Canal would be ideal as incubators where new industries could complete an initial stage of development, and later move onto larger premises. Thus building recondition and reuse was an early initiative for sustainability as was the concept of keeping the Old City as part of the working city of Montreal. Although today the tourist industry and residential development have taken over these sites, the plans continue to be a model of sustainability driven by the heritage value of the deep city.