The Arsenal de Metz is a 19th-century military arsenal converted in 1989 by the Spanish architect Ricardo Bofill into one of the great concert halls of Europe. The transformation kept the cathedral-like exterior of the original building and added a wood-panelled auditorium inside, with acoustics that critics rank alongside the Concertgebouw and the Musikverein.
It is the main classical music venue in Metz, with a programme that runs from chamber music to large orchestral works. Even if you can't catch a concert, the building is open during the day for free visits to the foyers. Combine with a walk through the nearby Quartier Outre-Seille.