Built during the 16th century by order of Elizabeth I for the Royal Navy, its primary aim was to protect warships at moorings along the Medway. Sadly, the castle was poorly maintained during the 1700s allowing a surprise Dutch raid to sack and destroy many ships berthed at Chatham.
Improved over the years, the fortress stands proud overlooking the river betwixt the villages of Lower and Upper Upnor, Kent, the later a quaint, cobbled village itself worth of an explore. At low tide the shoreline is dotted with ruins, the Saxon Shore Way runs along it. If you fancy a walk OS map 163 Gravesend and Rochester is the one to take. Upnor Castle is owned by English Heritage.