Fountain Creek Trail/Pikes Peak Greenway/Monument Creek Trail starts at Hanson Trailhead just off Grinde Drive in Fountain. It is a nice soft packed trail. It runs north between Interstate 25 and Highway 85/87 along the creek. Past Fort Carson, past El Pomar Youth Sports Park, and all the way to The Vanguard School. Here the trail becomes paved for several miles, past America the Beautiful Park, and into downtown.
Just past Bijou Street, it becomes soft again. It continues past the track at Colorado College, through Monument Valley Park, to the railroads tracks near Steel Street. Here it becomes paved again. Cross the tracks and continue around the five softball fields. The trail continues along Mark Dabling Blvd, past the skate park at Gossage Youth Sports Complex, past the Pikeview Reservoir, under Interstate 25 near the Rodeo Hall of Fame, and past Adventure Minigolf. This is as far as I ever ran heading north. I have been told it continues past Air Academy High School and the Air Force Academy.
Straight line distance from the minigolf to the trailhead is about 17 miles one way; with all of the twists and turns, it is easily 20+. If you continue all the way to the Academy it is quite a bit longer. You will cross quite a few bridges back and forth over the creeks. There are also numerous parking areas along the trail so you can start almost anywhere. You don't need to head all the way south to Fountain to get the trailhead.