One of the higher trails on Mt. Lemmon, Green Mountain begins with a short uphill into good, technical singletrack. There is always a possibility that you'll encounter large trees that have fallen across the trail you may have to climb over.
About halfway along the trail there's a longer uphill section, but not as steep, followed by a good amount of fun downhill along the hiking path with stairs to drop down. Watch for hikers along here and remember to yield.
There are a couple forks in the trail so be careful to follow the correct route unless you want to adventure. The ride ends at the General Hitchcock Picnic Area and easily links up with Bug Springs just down the road.