In this May 13, 2017 photo, a tree stretches into the sky on the drive up Flagstaff Mountain in Boulder, Colo. Part of what makes Boulder's 45,000 acres of open space and parkland so spectacular is that it's so accessible. One minute, you're dining, shopping or walking on a city street; five minutes later, you're up in the mountains, surrounded by pine trees, looking down on the city below. (AP Photo/Beth J. Harpaz)
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