East Bay Bike Path runs 14.5 miles from India Point Park in Providence, Rhode Island across the Seekonk River and all the way down to Bristol, paralleling the east shore of Narragansett Bay along an abandoned railroad route.
You'll get glimpses of Providence from across the river, a great view of Pomham Rocks Lighthouse from Riverside, and opportunities to stop in a handful of awesome parks.
Check out Haines Memorial Park in Barrington and Colt State Park in Bristol. The path also swings straight through a great Audubon property with a boardwalk that heads out to the bay. You can also easily swing through downtown Warren or Bristol. The majority of the trail is flat and very well-kept.