To the south of Castle Island is the Head Island Causeway. This is a sliver of land that is a walkway to teeny Head Island. Along the eastern side of the causeway are these, discarded granite pieces of gun mounts! Were these part of a water battery at some point, or were they carried all the way from the fort? Funny to think that, a century or more ago, some officer said, "these will be fine right here," and there they still are. Right there.