The Freedom Trail is a 2.5-mile-long (4.0 km) path through downtown Boston, Massachusetts that passes by 16 locations significant to the history of the United States. Marked largely with brick, it winds between Boston Common to the USS Constitution in Charlestown. Stops along the trail include simple explanatory ground markers, graveyards, notable churches and buildings, and a historic naval frigate. While most of the sites are free or suggest donations, the Old South Meeting House, the Old State House, and the Paul Revere House charge admission.