They put an observation deck in the top of the tower of the suspension bridge over the Penobscot narrows. We saw mountains 72 miles away. They had a full size display of a bridge section showing the structure too. Cool.
The Fort Knox (yes, just like the one in Kentucky…named after the same guy) Historic site includes a very good restoration of the fort that protected the narrows since the 1840s. It is one of the most fully restored forts we have visited and worth at least a quick visit.