Carisbrooke castle on the Isle of Wight - I am biased as I drive by it every day on the way to work and it always make me think of MTW. It saw a fair bit of action during our period including a crossbow sniping from the ramparts of the french general who was beseiging it. It is most famous for being the jail for Charles the first before he was beheaded after the Civil war in the 1600's - he had 2 unsucessful escape attempts including 1 where he was too fat to get out of the window - the price of good living!!