You can walk around the river or there're benches where you could sit and relax. Either way it's a great experience seeing the river and people walk by.
I went for a nice walk along the riveside with my boyfriend one night, it was dark and raining, but it was still so amazing, we got to see ducks sleeping and basically had the whole place to ourselves.
Watch the Fourth of July concert celebration and the Fireworks from the Esplanade. Or, rent a sail boat to cruise around The Charles or sail into The Harbor.
Whether you're relaxing on the docks or going for a long run, the Charles River Esplanade is one of the best places in Boston.
A great place for a long stroll from Back Bay to Cambridge.