This can be infinitely varied. Best thing to do is lengthen it. Extend your walk downstream to cross at the dam and upstream to cross at the BU bridge. Downstream there is a small embayment just northwest of the dam that is delightful. Crossing upstream at the BU bridge allows one to enjoy even more of the embankment on the Boston side.
It is always nice to take a walk along a body of water. Along the Charles you can run, walk, roller blade, bycycle , people watch, or fly a kite. There are walkways on both sides of the river. (that is the Cambridge side and the Boston side.) One of my favorite walks is from Boston University to Charles Street passing the Hatch Shell (where there are summer concerts)and Community Boating. (Sailing!) Plenty of Benches for sitting as well.
It's a nice walk but the path can get congested at times and there are a lot of bikes constantly going by on sometimes very narrow pathways. Still fun though and the Charles really does have a certain beauty to it. I'd recommend it for a nice leisurely stroll
I grew up with this area near my homes. This walk has been enjoyed by hundreds of thousands, including most students at Harvard, MIT, Bostaon Latin, etc. over the years. The Charles was somewhat unfairly immortalized in the classic 60's song "Dirty Water". It is a nice river with a nice walk, despite the surrounding traffic on major arteries on both sides of the river. Try to get there when the sailboats are out and the racing shells are practicing.