The Honmaru (本丸) (also spelled Hommaru) was the central, innermost part of the castle containing the donjon and residence of the shogun. The stately and luxurious main buildings of the Honmaru, consisting of the outer, central, and inner halls, were said to have covered an area of 33,000 square meters during the Kan-ei era (1624–1644). Surrounding the Honmaru were curtain walls, with 11 keeps, 15 defense houses and more than 20 gates.
Honmaru was destroyed several times by fire and reconstructed after each fire. The donjon and main palace were destroyed in 1657 and 1863, respectively, and not reconstructed. Some remains, such as the Fujimi-yagura keep and Fujimi-tamon defense house, still exist.
The Honmaru was surrounded by moats on all sides. To the north separating Honmaru from the Kitanomaru were the Inui-bori and Hirakawa-bori, to the east separating the Ninomaru was the Hakuchō-bori, and to the west and south separating the Nishinomaru were the Hasuike-bori and Hamaguri-bori. Most of these still exist, although the Hakuchō-bori has partly been filled in since the Meiji era.
Read more about this topic: Edo Castle