Gateway, a postern (secondary) entrance, built 1220's by Hubert de Burgh after Louis VIII's 1216 Great Siege of Dover Castle. Beaked shape strengthens base of flanking towers against mining. Also a BBC TV "Doctor Who" set location. Forbidden Zone view from Counterscarp (outer moat embankment). Norman Listed Building, English Heritage site, and Scheduled Ancient Monument. Medieval History, Travel, Tourism, and Vacation.