Try Denver's New Trail
It’s not every day you get a new trail close to home to explore. Technically, these were existing trails that someone had the idea to link as a big circle around the greater metro area.
The Denver Orbital Trail (DOT) is an urban adventure best done in segments as it is 177 miles total. Read more about my attempt at one of these segments with some friends in this Denver Post article. Make sure you have a map and some navigation skills for this outing!