Long before American architects started yammering on about sustainability, the Danes were inserting natural daylight into every last recess and building shared courtyards in housing complexes that unself-consciously muddied the line between public and private spheres. Sustainability wasn't just a byword of the environmental movement; it had powerful social implications, encouraging all sorts of people to brush up against each other -- which is precisely what you'd expect from the country that has the slimmest gap in the world between rich and poor.

Today, Denmark continues its fine tradition of designing for posterity, but with a twist. The functionalist boxes that characterized mid-century Modernism have given way to weirder geometries (hej hej, right angles!), and the unadorned facades favored by the likes of Arne Jacobsen -- Denmark's towering National Treasure, second only to Hans Christian Andersen and maybe Viggo Mortensen -- are invented anew in splashy, offbeat cladding. The new aesthetic affirms, without salaaming to, the region's fetish for green living. Here, we present five Danish architects toiling at the crossroads of old Scandinavian ideals and sexy new design. Memorize their names. They're changing Denmark and, in some cases, the world.

3XN is a 24-year-old firm headquartered in Copenhagen. They bill themselves as space therapists of sorts, asserting that architecture shapes behavior, down to whether or not people greet each other at the water cooler. So for one of their recently completed projects, they managed to get the world's most anti-social professionals to talk to each other. We speak, of course, of lawyers.

These are the new Copenhagen headquarters of Horten, an employment and labor law firm. The prefab travertine facade allows in bands of light (as required by Danish law) while minimizing heat gain. That way, you don't have to blast the AC in the summer.

But the real feat is this: Indoors, there's a central staircase that everyone tramps up and down, so you can't just slip into your office unnoticed. "Even though they are lawyers," principal Kim Herforth Nielsen tells us, "they have to interact, too."

3XN was recently featured in Mind Your Behaviour, a solo exhibit at the Danish Architecture Centre. Here's one of the projects highlighted in the show -- an aquarium, shaped like a whirlpool. Watch out, it'll suck you in!

Effekt is a small, young architecture firm based in Copenhagen. This is their forthcoming visitors' center in Hareskoven, a forest outside the city and the erstwhile "hunting grounds for the king." (Which king, we're not sure.)

The building's shaped like a star to ape the "the pathways of the forest that surrounds it," and its roof dips down to the ground in a couple places as if it were sewn into the landscape. The center's expected to be carbon neutral.

At the opposite end of the age spectrum is Vilhelm Lauritzen Architects (VLA) nee 1922. They designed the main building at Copenhagen Airport (then Kastrup), which opened for business in 1939.

The firm is still designing Copenhagen's airport. Here's their newest addition, a terminal for budget carriers.

VLA is firmly rooted in Danish Modernism, but still manages to produce some interesting contemporary stuff. This is an amateur football clubhouse in Copenhagen's equivalent of Central Park. Note the skewed volume -- an update of the traditional Danish box -- cantilevered over a green roof that dips down to street level. Even sweaty locker rooms can be pretty!

Bjarke Ingels is probably the most famous architect working in Denmark today. He attracted loads of attention for a pair of chunky utopian housing complexes -- one shaped like a mountain, the other like the letters "V" and "M" -- that he designed for a new neighborhood development (now largely on hold) in Copenhagen. The buildings hew to some basic tenets of Nordic architecture, like openness and access to natural light, but they look completely -- wonderfully -- unhinged. Ingels has since gone international, injecting aspects of his eco-hedonism, as he calls it, into everything from the Danish pavilion in Shanghai to a women's sports center in Sweden (pictured here) to a national library for Kazakhstan's omnipotent ruler. The latter project hints at the difficulties of exporting Danish design. Can architecture be socially responsible in a country under dictatorial control? Or does it become just an authoritarian plaything? Call it the Albert Speer dilemma.

This is the Taiwan Twirl House -- a kind of architectural interpretation of a Lucio Fontana canvas -- by Ingels's former partner and co-collaborator on the VM Houses Julien de Smedt. De Smedt (who's actually Belgian, but works in Denmark) started his own firm JDS Architects in 2006.

Like Ingels, he's trying his hand at large-scale international projects. Here's his proposal for a "wellness island" somewhere (not specified) in the Middle East. It includes a spa, a marina, gardens, a hotel, apartments, and a cinema.

OK, so a project like this probably isn't going to change the world. But it certainly highlights another aspect of Danish culture us Yanks could use more of: leisure time.