29.22 km 95859.43 feet 18.16 mi 8518.00 seconds 141.97 minutes 2.37 hours 7.67 mi/hr
Ithaca's Black Diamond Trail is not completed yet. The most important work, putting the two missing bridges back, has been completed. However, the trail surface is wanting improvement in some places, as the signs make explicit: "Not suitable for a trail or any other purpose." However, if you're persistent, you can make it all the way up the hill from Ithaca to Tunkhannock Falls State Park.
The trail seems to be routed down to the parking lot for the falls, but if you continue on the railbed, it will take you across two bridges. The first one gives you an awesome view of the upper (smaller) falls and associated gorge. The second one is a small bridge over an even smaller former highway. The trail ends at this point. North of Trumansburg the railbed has been plowed away.
Because the trail isn't really finished, I chose to ride back on the highway. I think that may be the most enjoyable route even though there are some hills. The shoulders are good until you get within the Ithaca city limits, at which point you'll want to take the lane because there is no shoulder at all, and you can easily coast at 30MPH, and damn the cars behind you that want to break the speed limit.