Also known as Gillingham Fort, this artillery fort, was `in a recognisable state of decay’ in 1806. No recognisable remains, the site is now occupied by Gillingham pier.
The village stands on a hill overlooking the Medway, two miles N.E. of Chatham ; and on the shore of the river below are the ruins of a fort, built in the reign of Charles I. for the defence of the dockyard and fleet. The only occasion on which this fort came into notice was in June 1667, when the Dutch invasion of the Medway took place, as related in the account of Upnor Castle (q.v.) ; but as the armament was but a battery of four serviceable guns, it had little effect in checking the onset of De Ruyter and Van Gent, when, after taking Sheerness, they passed the chain at Gillingham, and proceeded to destroy the English ships of war.
This fort, though enlarged and dignified with the natne of castle, was never of any military utility. (Castles Of England, Sir James D. Mackenzie, 1896)
like to know details of ruins of Gillingham castle
As I would understand, as in many cases there is nothing much left. Try the local tourist offices or Pastscape http://www.pastscape.org.uk/ is very good.