The design of One & Ortakoy is driven by the rules of a maximum volume allowed to build. Construction regulations seem to be bonded to area and heights, but actually it is the volume that values the building. The solution is arranging the so given fixed-volume according to the needs of the containing shell. When there is a space using more volume the other spaces reacts, shrinking to an optimal value. Multiple parameters such massing and arrangement, enclosure of the environment, harmony with topography and landscape as well as the prospect for each unit affect the design. Considering these impacts whilst differentiating and the simultaneous analysis of different typologies were solved via simulation and a constant evolution of the building and by that a main part of the design process. The project consists out of two building blocks, a separate residential and a mixed used part. The heights of these two blocks are melting into each other by using the same language both in the roof gardens and the facade. The project is not only shaped by an amorphous form but also using the seemingly randomness created by the diversity of different user choices for flats and by that brings a new level and quality to housing. The entire roof is used as a recreation area; walking and jogging trails, a pool and green spaces are implanted while other elements of the building become compact. On top of adding recreational qualities to the building, the green roofing reduces the carbon emissions in a maximized surface of the buildings – a much needed approach to contribute to the environment and in its nearby context at the same time adapting the surrounding topographical differentiations, to merge with it and fit in. The recently completed construction of the project proves that erecting the building is not only the mass. It is rather the extension of nearby green spaces on the roofs of the buildings that makes the project a living organism in its habitat. In order to maximize the integrity of the environment from bottom to top, terrace gardens, assigned to each of the apartments and duplex connect ground and roof of the building, increasing the total of the building by 2,500 m2.