If you want to get your blood flowing a bit, start at Roger Williams Memorial on Congdon St, (near downtown) and walk uphill on Bowen Street. You'll get a feel of all the different terrain of the city, sidewalk, cobblestone, asphalt, and urban trail. When you take a right after the dirt path, you'll be able to see the entire PVD skyline. Depending on the bus/train you take to get to PVD from Boston, you might just be let off at the Memorial.

It is important to know that there is a Roger Williams Park and a Roger Williams Memorial. This Memorial is very close to the downtown, while the park is much farther away, but also worth the trip.