Using the architectural urban structure of Vienna as a basis, the project “Pocket Mannerhatten” examines the question how sensible synergies between individuals and large-scale investors can be found as part of the process of urban agglomeration. It confronts the challenge of fragmented building lots and offers concepts for re-condensing and using these in an orderly, cooperative form. The development strategy is based on the swapping and sharing of usage rights for various parts of a building. Several parcels of land are jointly used by a neighbourhood as a “collaboration cluster” which shares core infrastructure, underground garages, inner courtyards, common spaces and roof gardens. Since coordination takes places before the planning process, this makes very different urban-planning and architectural solutions for a new building or a renovation possible. This collaboration is optional and is tied to a bonus in the form of additional cubic capacity for which building permissions are available. Anyone collaborating and working in favour of the collective receives additional building options, according to this concept. “Pocket Mannerhatten” strives for a form of urban development designed by residents themselves and accompanied by municipal administration. Especially existing neighbourhoods, such as the late-19th-century quarter of Ottakring (Vienna, Austria), are to be improved by mixed usage and the creation of public green and recreational spaces as well as vibrant neighbourhood communities.