Operating at the juncture between various disciplines—architecture, landscape, history, technicality, humanities—rooftop gardens are located on the roof terrace of a building and host plants by being both above and beneath, using the underlying architecture as a new ground surface. They extend like a blanket of vegetation, while also sheltering a living area. Whether set up due to a religious motive, a desire for representation, the practicality of providing food, or simply as the result of spatial constraints related to the high-density environment, these gardens are unusual and fragile, and their existence would have been impossible without human intervention. More complex to build, they nevertheless seem to have always existed.
Plants have been installed on roofs throughout the history of architecture. As unique as the examples of rooftop gardens might be, they are always the result of an extraordinary determination that defies technical and geographical complexities and is probably driven by the idea that a rooftop garden isn’t like other gardens, both in how it is perceived and in the perception that it offers over the horizon.
Rooftop gardens first appeared in the Middle East, before spreading into Europe during Antiquity, firstly in Italy, where major rooftop gardens were built during the Renaissance, and later in France, notably in the Parisian hôtel particulier mansions of the seventeenth and eighteenth centuries. Probably due to the complexity of construction and the limited means of the times, rooftop gardens remain exceptional creations, unique and isolated pieces of architecture. They were frequently created as a performance, perhaps as an expression of religious, political, or economic power. Whether landscaped gardens, formal French gardens, kitchen gardens, groves, or luxurious meadows, having a planted area on a rooftop creates conditions that exist nowhere else.
Given our social and environmental concerns, rooftops gardens challenge the distinction that is made by most urban designs, which aim to separate the stone world of the city from the world of the living. Rooftop gardens are the very figure of the reunion of these entities. They are of particular interest to us because they might be a key component of the resilient city, enabling humans to reconnect with their environment without pitting the city against nature; but also because they provide an opportunity to question the architectural project, the cityscape, and its relationship to the landscape. Indeed, the boundary that typically defines a garden is called into question by a more abstract border related to its height. In other terms, rooftop gardens appear to extend beyond their enclosure questioning the very notion of the hortus conclusus.