Canterbury Castle is a significant historical structure located in the heart of Canterbury, Kent, United Kingdom. This medieval ruin once stood as a symbol of royal power and defense, playing an important role in England's Norman heritage. It was one of the three original castles built by William the Conqueror in the 11th century, primarily to consolidate the Norman hold on the region. Constructed from local Kentish ragstone around 1070, the castle has gone through various stages of development and decline over the centuries. The original motte-and-bailey design was eventually replaced by a stone keep. During the First Barons' War, the castle endured a lengthy siege, leading to substantial fortifications. In subsequent years, its military significance waned, and by the 16th century, much of its stonework was repurposed for new local structures. Despite its ruins, elements like the rectangular keep's thick walls and partial surviving structures give visitors a glimpse into its past grandeur. Today, Canterbury Castle is maintained as a historical site. Its remnants continue to attract visitors, enabling them to feel connected to England's rich history while enjoying a green, open space in the city.