The Black Diamond Trail is a local classic. It takes you from the Ithaca Children's Garden (a great spot in its own right) up to the overlook at Taughannock Falls, at a very steady 2% grade on very well maintained tightly-packed gravel.
Tip: if you need to use the restroom at the top of the trail, there's a visitor's center down the road a short walk or ride away (2381 Taughannock Park Rd).