This is a very popular hiking loop as it's within walking distance of the Cold Spring train station and very accessible from NYC, and popular with the local trail running community. It has some really great views and varied terrain. It is well marked - follow blazes white to blue to red to blue. The lower part of white Washburn trail has recently undergone significant trial improvements including gravel grading to the old quarry, and stone steps just past the Cold Spring overlook. They were working on them when I passed them today. About 3/4 mile into the ascent the trail transitions into rocky single track. After the summit its a very runnable descent, though there's a fair amount of rock garden on the blue and red. The blue Cornish trail is graded and turns to asphalt after the ruins. A sign brings you back onto single track for a return to the parking lot. I start and stopped my watch at the gate
In the late fall of 2020 the blue trail was reconfigured to bypass a gnarly rock section. There's an older Strava segment that is no longer picked up because of this bypass, but for historical times it can be found at https://www.strava.com/segments/21147811?filter=overall .