National Geographic : 1947 Feb
.- a U.S.Navy-National Park Service In the Midst of the Gulf Stretches a Wet Moat, an American Fortress's Medieval DefenseAgainst Raids and Jail Breaks Fort Jefferson's only entrance, the bridge and sally port (front), once had a drawbridge. Legend says sharks were enticed into the moat todeter escaping prisoners. Six huge corner bastions could sweep the ditch with fire. On the parade ground are the caretaker's house (left), officers' ruined quarters (center), and soldiers' barracks (right).