Dating back to 1807 and the only remaining signal tower in North America, the Portland Observatory is one of the most iconic and historic structures in the city. This seven-story red-brick building offers panoramic views of the city, the Portland Harbor and the Atlantic ocean in the distance. Guided tours are conducted every day and give you an insight into the history, culture, and workings of the city in the early days. The Observatory is extremely interesting and a must-visit when in the city.