The Royal Citadel is a historic fortress located in Plymouth, England. Built in the 17th century, it was designed to protect the naval port from potential attacks. The citadel features impressive walls and bastions, showcasing military architecture of its time. Today, the Royal Citadel serves as a base for the Royal Marines and is an important site for military heritage. Visitors can explore its grounds and learn about its history, including its role in various conflicts and its significance to the British Navy.