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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17. Portchester Castle memories
Portchester Castle being excavated circa 1930. Picture: The News, Portsmouth Photo: The News archive
18. Portchester Castle memories
Scenes from the Mini-Medieval display at Portchester Castle on July 31, 1995. The News PP3907 Photo: The News archive
19. Portchester Castle memories
Two Roman Praetorian Guards at the entrance to Portchester Castle on June 25, 1990. The News PP3908 Photo: The News archive