The project chooses open air public space as the protagonist of the proposal, creating a city space with collective and meeting life. It's an optimistic proposal for this vital space in the heart of Paris. We chose the cylindric shape as a formal tool and we repeat it on the whole proposal. This offers the possibility to diversify and to individualize each cylinder. The cylindrical shape occurs untill the construction elements: lifts, stairs, façades, floors. The wish to limit the built volume allows us to think a new concept based on the share of uses, to maintain construction and maintenance effective-costs.