The Salle Proton (Proton Hall) used to be the rehearsal room for the Orchestre national de Lyon and is now the Auditorium’s second concert hall. Known formally as the Salle Proton de la Chapelle, this novel venue has a magnificent prestressed concrete cathedral ceiling typical of 1970s architecture. It is now used as a concert venue for small-scale concerts and other small and atypical events, in particular during the Auditorium’s theme weekends.