At the far north western end of the outer curtain wall of Dover Castle is a group of five towers which once formed the north entrance to the castle. These were originally constructed late in the reign of King John (1199-1216) but were substantially rebuilt after the French siege in 1216/17 when it was blocked and new entrances were created in less vulnerable locations; the towers were later modified to carry a Napoleonic battery. (location accurate to the nearest 1m based on available information)