It is one of the best preserved Saxon forts and its lofty position on the south coast made it a perfect part of the defence strategy for the Solent for hundreds of years.
Over the years the castle has also been a favourite with historians and re-enactments, which regularly take place within the stone walls.
Here are some of our favourite memories of Portchester Castle.
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5. Portchester Castle memories
More than 60 members of the English Civil War Society's Fairfax Battalia were battling it out at Portchester Castle on October 7-8, 2006. The News PP3904 Photo: The News archive
6. Portchester Castle memories
Portchester Castle from Horsea Island, January 1970 Photo: The News archive
7. Portchester Castle memories
Norse men at Portchester Castle April 17, 1995. The News PP3905 Photo: The News archive
8. Portchester Castle memories
Queen Elizabeth I is one of the chararcters in a history through the ages presentation at Portchester Castle (undated). The News PP3902 Photo: The News archive