Today my son (26) and I rode the entire length of the OCA Old Croton Aqueduct, from Riverdale to the Croton Reservoir.
34 miles @ 11mph, 1700' and 1800c
I did it on my CX and the trail is mostly a narrow dirt strip with lots of rocks, roots and other obstructions. Some sections required us to use public streets and the trail is not very well marked. Anyway, i'm exhausted and it was a great experience.
https://www.strava.com/activities/768046120