I have always liked walking this bridge which goes over the Passagassawakeag River. You can take the quick way to this cache by driving down Footbridge Road. There is also the new "Belfast Boardwalk" which starts on the other side of this bridge which I also recommend.
You are looking for a black tube almost five inches long, with a green geocaching sticker on it, hidden out of sight. Although the actual cache cannot be seen you should see what you need in order to find the cache. Please relace it exactly as you found it. BYOP. I hope that this cache lasts, as it is at a great spot to walk, or to just enjoy the view.
UPDATE 10/1/2016 THE OBJECT THAT HAS BEEN STATIONARY SINCE 1921 HAS BEEN MOVED AND THE CACHE MOVED WITH IT!!! Please use extreme stealth when looking for this cache now and please be sure that you put the cache in the same pipe that you took it out of, (the middle pipe in the back with the magnet over it), and do not shove it up a different pipe. If you need any force then you are doing it wrong.