Peel Castle is a ruined medieval fortress on St Patrick's Isle, connected to the town of Peel by a causeway. It was one of the two principal garrisons of the Isle of Man and the site of the Cathedral of St German. Edward Christian was held prisoner within its walls for approximately eighteen years, and during the 1651 rebellion the northern companies besieged the castle while Charlotte de la Tremoille negotiated her own surrender terms with the Parliamentary commissioners.