Castra of Felixstowe
United Kingdom
Walton Castle was a Saxon Shore Fort in the Roman province of Britannia. The fort was reused by the Normans who used it as the bailey for a castle. It stood 30 metres above sea level but was destroyed by coastal erosion in the 18th century. It was located in the village of Walton, Suffolk, now part of Felixstowe (grid reference TM32253580).
Archaeological site data from Wikidata (CC0). Summary from Wikipedia (CC BY-SA).