These jaw-dropping rock walls flanking Green Mountain have become the symbol of the city, with many Boulder businesses ... still take in the Flatirons from one of the area's hiking trails ...

Today, Boulder retains its charm at the foot of the sandstone Flatirons, a foothill range crisscrossed by hiking trails that begin at the Colorado Chautauqua, a cultural and performing arts hub ...

Today, Boulder retains its charm at the foot of the sandstone Flatirons, a foothill range crisscrossed by hiking trails that begin at the Colorado Chautauqua, a cultural and performing arts hub ...

FILE - The Flatirons mountain formation lies dusted white after a night of light snowfall, in Boulder, Colo., on Nov. 17, 2015. (AP Photo/Brennan Linsley) ...