THE25 is an exhibition, relaxation and communication space. It consists of a open space with a central bar, framed on one side by a meeting room and on the other by a terrace. A service hallway serves as a library and accommodates the utilities (toilets, mechanical room...). All of this is illuminated from above by a sawtooth roof as the site is firmly wedged into the existing urban fabric. The building was built on top of three basement levels. In order to encourage the use of the lower level areas (even during construction), the structure of the new building has been reduced as much as possible, hence the use of a prefabricated metallic trellis structure. The main challenge of this project was to work on urban densification in Paris, how to offer new spaces to live, in a saturated fabric.