Could it be city walls rather than a castle? There is a fire station next to the entrance isn't there?
Does it look to others,as it does to me,that there is no passageway through the arch,the shape visible below the apex being a hole in a wall beyond,i.e.it is a decorative rather than a functional arch?RegardsRoger
LV 1600 (if that is what it is) was issued from July 1932 to Aug. 1934 by Liverpool Counci