My favorite trail for biking and hiking is the former towpath of the Ohio and Erie Canal. It’s mostly flat, there are numerous places to take a break, and it’s long enough (Cleveland to New Philadelphia) for incremental rides or hikes.
When the canal was constructed in the early 19th century, it connected the Ohio River at Portsmouth with Lake Erie at Cleveland. Shipping via canal boats was supplanted by rail cars, which were faster and not limited to waterways.
Nowadays, you will have plenty of company on the trail among bikers, hikers, skaters, bird watchers and dog walkers.