To reach Fort Knox State Park, you must cross the Penobscot Narrows Bridge. Do not be in hurry to drive across its 2,120 foot length. The cable-stayed bridge was finished in 2007 at a cost of $85 million. An elevator will take you up 42 stories. The 420 foot tower of the Penobscot Narrows Bridge is the world’s tallest bridge observatory. The panoramic views at that height are incredible.