As 2015 came to an end, 195 of the world's nations came together to adopt a major plan for tackling climate change.That landmark agreement, reached after two weeks of negotiations at the United Nations' COP21 summit in Paris, is a big deal for the future of the planet.But sometimes, the battle against climate change starts at the local level. Many individual cities and communities have led the way in creating projects and initiatives that promote environmental sustainability.That's not a surprise to Max Young, vice president of global communications and marketing at 100 Resilient Cities, an organization that helps cities prepare for " physical, social, and economic challenges ," including climate change. The reason, he says, is simple: "cities can act.""Whether it's controlling a police force or a transit system, cities are not paralyzed by politics — most times, they're pragmatic," Young, whose group brought together mayors from around the globe to participate in a "Resilience Day" at COP21 , explained to Refinery29. "If you look at the federal governments around the world, they're polarized and paralyzed by politics. Cities, by and large, don't find themselves in that situation."From a mesmerizing pedestrian bridge in Copenhagen to Rotterdam's storm-drainage system — which doubles as a park — we've rounded up some of the best ways that individual cities are paving the way in the fight against climate change.