Flagstaff Mountain is a foothill on the eastern flank of the Front Range of the Rocky Mountains of North America. The 6983ft peak is located in Boulder Mountain Park, 5.6km southwest by west (bearing 239°) of downtown Boulder in Boulder County, Colorado, United States.MountainFlagstaff Mountain offers scenic day and night views of Boulder, Metropolitan Denver, and the surrounding mountains. There are hiking and bike trails, picnic areas, the Summit Nature Center, and an outdoor amphitheatre.