The Penobscot Narrows Bridge Observatory can be accessed at Fort Knox State Park in Prospect, Maine.
Taller than the Statue of Liberty the bridge observatory offers 360 degree views of the Penobscot River. It is the tallest bridge observatory in the world. An elevator whisks you up to the observation deck for spectacular views.
You can see the adjacent Fort Knox from the observatory be sure to pay the fort a visit on the way out.
This bridge replaced the Waldo-Hancock Bridge which was also quite picturesque in its day.
A small roadside pullout has good views of the new bridge and some history on the old bridge.
Make a point of seeing both the bridge and fort on your way to Downeast Maine.