The Flatirons are rock formations in the western United States, near Boulder, Colorado, consisting of flatirons. There are five large, numbered Flatirons ranging from north to south along the east slope of Green Mountain, and the term "The Flatirons" sometimes refers to these five alone. Numerous additional named Flatirons are on the southern part of Green Mountain, Bear Peak, and among the surrounding foothills. The rocks themselves are between 290-296 million years old. They are a popular rock-climbing location, with Mountain Project listing 1,427 climbing routes in The Flatirons. Many gather at Chautauqua Park in Boulder at the base of The Flatirons to enjoy the natural environment, preserved by Boulder Parks and Recreation. The Flatirons are an iconic symbol of Boulder, serving as the city's signature backdrop, emphasizing the culture of adventure.