The Tokugawa shogun's Kyoto home stands in stark contrast to most of Japan's other remaining castles, which were constructed purely for defense. Built by the first Tokugawa shogun, Ieyasu, in 1603, Nijo Castle, a UNESCO World Heritage Site, is considered the quintessence of Momoyama architecture, built almost entirely of Japanese cypress and boasting delicate transom woodcarvings and paintings by the Kano School on sliding doors. Unfortunately, no photos are allowed.
I prefer Nijo Castle to the Imperial Palace because you can explore its interior on your own. The main building, Ninomaru Palace, has 33 rooms, some 800 tatami mats, and an understated elegance, especially compared with castles being built in Europe at the same time. All the sliding doors on the outside walls of the castle can be removed in summer, permitting breezes to sweep through the building. Typical for Japan at the time, rooms were unfurnished, and the mattresses were stored in closets.
One of the castle's most intriguing features is its so-called nightingale floors. To protect the shogun from real or imagined enemies, the castle was protected by a moat and stone walls. How deep the shogun's paranoia ran, however, is apparent by the installation of these special floorboards, which creaked when trod upon in the castle corridors. The nightingale floors were supplemented by hidden alcoves for bodyguards. Furthermore, only female attendants were allowed in the shogun's private living quarters. Ironically, it was from Nijo Castle that Emperor Meiji issued his 1868 decree abolishing the shogunate form of government.
Outside the castle is an extensive garden, designed by the renowned gardener Kobori Enshu, which is famous in its own right. The original grounds of the castle, however, were without trees -- supposedly because the falling of leaves in autumn reminded the shogun and his tough samurai of life's transitory nature, making them terribly sad. Plan on spending 1 1/2 hours here, especially if you decide to rent an audio guide for ¥500 extra, recommended because it describes the significance of what you're seeing.