< ">Denmark's capital rarely gets the attention it deserves, so it's been quietly focused on sensible city planning with comprehensive bicycle paths, free bikes, and a new metro line in the works to deal with the expanding city center. Residents are also trying on a host of new public buildings -- an opera house, a cutting-edge library, and a concert hall -- and an environmental program that's turning the rest of Europe green with envy. And despite the often gloomy northern climate, residents are routinely rated as some of the happiest people in the world. They'll have the opportunity to show off their city when it hosts the COP 15 Climate Change Conference in December 2009, a high-profile, international assembly of politicians looking for ways to reduce greenhouse emissions. They won't have to look much further than the host city for compelling ideas.