Ride up nice open meadow for half a mile until you hit dense forest that is surprisingly healthy (it's mostly NOT lodgepole pine, which are all dying from pine bark beetles). There are a few rocks here, but it's easy and wide.
Enjoy the cool, moist trees and climb gently to a low saddle. Then descend through a series of boggy meadows. The trail is well designed and stays dry despite the marshy sections. This part has great views of Quandary Peak (14,265') and other big mountains in the distant Ten Mile Range. There are many trails here, but they are well signed. Fun and scenic!
You eventually arrive at a historic homestead. Poke around and then continue on Keystone Ranch Road just a bit until you find singletrack go up the hill and meet West Aqueduct Trail and Red Trail.
The trail has been extensively rebuilt in recent years to make it more sustainable.