 Little is known about the design of the first castle at Rochester as it has since vanished , and even the exact site is uncertain . It most likely took the form of a motte @-@ and @-@ bailey castle , with a mound and an outer enclosure defended by a timber palisade and earthen banks . Boley Hill has been suggested as the site of the first castle , an outwork reinforcing the castle 's defences , or an abandoned siege castle like those documented in the 1088 siege . Boley Hill is a natural outcrop of rock , and could have acted as a motte . 
