 The Penobscot Bridge site also is home to the Penobscot Narrows Observatory, the first bridge observation tower in the United States and the tallest public bridge observatory in the world.The tower reaches into the air and allows visitors to view the bridge, the nearby Fort Knox State Historic Site, the Penobscot River, and Bay.The Penobscot Narrows Observatory opened to the general public on Saturday, May 19, 2007.