Since the emergence of lifts in the mid-19th century, the penthouses of buildings in large cities have gained in prestige. However, most of their rooftops remain empty and totally unused. This book uncovers one of the most interesting and ingenious architectural trends of recent times : remodeling of the underutilized spaces on the roods of buildings. Through photographs, drawings and texts, Cloud 9 Roof-top Architecture presents surprising dwelling modules created on rooftops, private terraces turned into chill-out zones and hotels that are building swimming pools and gyms on their roofs for the enjoyment of their guests. These projects are daring designs that once again reveal the infinite genius of architects and designers. And if we look beyond the architectural value of these projects to look at the overcrowded nature of large cities, the use given to these spaces reveals a more rational, sustainable and intelligent application of architecture.