Fort Warren is a historic coastal fortification located on George's Island in Boston Harbor, Massachusetts. Built between 1833 and 1860, it was designed to protect the harbor from naval attacks. The fort features a distinctive star shape and is made of granite, with thick walls and numerous gun emplacements. During the American Civil War, Fort Warren served as a military prison for Confederate soldiers and other prisoners. Today, it is a popular tourist destination, offering guided tours and educational programs about its history and significance in American military heritage. Visitors can explore the fort's structures and enjoy scenic views of the harbor.