Like many university campuses, the École polytechnique fédérale de Lausanne (EPFL) developed at a distance from the city whose name it bears. This geographical separation reflects a deeper divide: knowledge often remains confined within the campus, with limited connection to the city and its inhabitants. At the other end of Lausanne, Bel-Air 4, the former headquarters of the BCV designed in 1973 by architects Marcel and Jacques Maillard, embodies another form of disconnection: a central and visible building, yet long abandoned and commonly referred to as “la verrue.”

Although seemingly opposed, these two situations are linked by the same infrastructural line: the M1 metro. This direct connection allows EPFL to re-establish a tangible presence in the city centre. Conceived as a relay, the project transmits the dynamics of the campus to the city. It hosts exhibitions, lectures, and debates, but more importantly, it functions as a permanent interface between the institution and urban life.

Facing the street, the existing building is preserved to accommodate the more introverted programme: offices, study rooms, and guest housing. Toward the courtyard, a new public volume is inserted into the available space, on the footprint left by the former printing house.  The intervention requires opening up the building to introduce natural light and ventilation into the new spaces. Large openings are cut flush with the concrete façade on the courtyard side, reactivating its architectural presence. The façade is then reinterpreted through a reversal of roles: what was once exterior becomes interior, while the newly constructed volume extends the existing building into the courtyard.  A steel structure is first erected in the courtyard to stabilise and support the existing façade. The ribbed concrete slabs are then cut into modular elements and reused as floor plates, placed onto the beam grid of the new steel framework on the opposite side of the façade. Space thus shifts sides through the physical displacement of structural components.

Rather than a logic of replacement, the project is grounded in transformation. Existing elements are retained, displaced, and reassembled, not as static traces of the past, but as active materials within the project. Reuse becomes a central constructive strategy, structuring both spatial organisation and architectural expression. Through this inversion of uses and boundaries, a specific atmosphere emerges, suspended between interior and exterior, between the existing building and the addition. The project thus establishes an in-between condition, where transformation becomes legible and a renewed relationship is constructed between the building, its site, and the city.