The most striking modern building in the capital of Norway proudly identifies itself as the Oslo Opera House. Yet a more democratically accessible building in this hereditary kingdom would be difficult to imagine. When I paid my first visit last year, young people were dangling their feet in the water from its roof. Yes, its roof. In an audacious move, the Norwegian architectural firm Snohetta extended the roof line right into the city’s harbour, creating an enormous sloping public space, regularly inhabited by citizens and non-citizens alike.