Théâtre Sébastopol is one of Lille's main performance halls, with a handsome early 20th-century auditorium and a programme that ranges from concerts and comedy to dance and touring theatre. It is less monumental than the opera house, but it is often where locals actually go for a night out.
Check the calendar before treating it as a sightseeing stop; the building is best experienced with a ticket. Its location southwest of the Grand Place makes it easy to combine with a city-centre evening rather than a separate expedition.