Nestling in a deck-chair, looking up at a huge open-air screen as the stars come out and finding yourself gasping or laughing out loud with a couple of hundred other people is just the tonic for a balmy summer evening. Especially if it's in an original location like the esplanade of the natural history museum in Brussels, where the free PleinOPENair festival of film and music kicks off on 30 and 31 July.