Ninomaru is a term that refers to the inner citadel of a Japanese castle, particularly in the context of the Nijo Castle in Kyoto. It served as the residence of the shogun and was designed for both defense and administrative purposes. The Ninomaru area features beautiful gardens and traditional architecture, showcasing the elegance of Edo-period design. The Ninomaru Palace, located within this citadel, is known for its stunning sliding doors and intricate woodwork. It is a UNESCO World Heritage site, reflecting the historical significance of the Tokugawa shogunate and the cultural heritage of Japan. Visitors can explore its rooms and appreciate the artistry of the period.