MNN - Mother Nature Network

Which major U.S. cities offer the best accessibility to nature? Which have the most vibrant environmental cultures? If you love to hike, bike, ski, raft or climb while still appreciating the amenities of urban life, a few of our nation's concrete jungles offer a little bit of everything for the modern outdoors enthusiast. Here's our list of America's best cities — some big, some small — for exploring the outdoors.