Oslo Opera House

This is the only opera house in the world where you're encouraged to walk on the roof. Snøhetta's masterpiece rises from the Oslo waterfront like a glacier calving into the fjord — white Carrara marble and Norwegian granite angled so that the building itself becomes a public plaza. On any given afternoon you'll find teenagers skateboarding on it, couples watching the sunset from it, and tourists trying to figure out whether they're standing on a building or a landscape. The answer is both.

It opened on 12 April 2008, the largest cultural building Norway had constructed since Nidaros Cathedral was finished around 1300. The numbers are staggering: 38,500 square meters, 1,100 rooms, a main auditorium seating 1,364, and a construction budget of 4.4 billion kroner that came in 300 million under budget and ahead of schedule — possibly the only mega-construction project in history to pull that off. Snøhetta beat 350 other firms to win the design competition in 2000.

The building transformed Bjørvika from derelict docklands into Oslo's cultural heart almost overnight. Before the opera house, this was a wasteland of container terminals and highway overpasses. Now it anchors an entire waterfront district. The plaza in front is named after Kirsten Flagstad, the legendary Norwegian soprano who was one of the greatest Wagnerian singers of the twentieth century. Inside, Olafur Eliasson designed perforated panels with hexagonal openings that glow like melting ice.

In its first year alone, 1.3 million people visited. It won the 2009 Mies van der Rohe Award for the best building in Europe. Walk up the roof, stand at the top, and look back at the city. You're standing on Norway's answer to the Sydney Opera House — except this one, you can climb.