Built in 1915, this lightship guided other ships to safety until 1964. "Portsmouth" remains one of a very few lightships still intact. Lightships, before modern technological advances, were used in areas where unsuitable conditions wouldn't allow for a lighthouse but a guiding light was still needed. Mainly used on the East Coast, lightships remained in use until 1985. Small and unique, "Portsmouth" is a fascinating piece of history and a good way to spend 30 minutes.