Edo Castle was the last and greatest of the Japanese Castles, begun at the behest of Tokugawa Ieyasu in 1603 and completed in 1637. It was constructed at a time when castles were becoming less necessary as actual fortresses, and more important as symbols of a daimyo's wealth and power. As the wealthiest and most powerful daimyo ever, Ieyasu set out to build the largest castle in Japanese History in the very center of his new capital at Edo, although the castle was not completed until well after his death.
The six story tenshu or main keep was almost two times as large as the largest surviving keep at Himeji Castle, and one-and-a-half times as large as Tokugawa Hideyoshi's keep at Osaka Castle. The castle towered over the city of Edo, and could be seen for miles around.
Japanese movies and TV dramas are very fond of showing Edo Castle in establishing shots to instantly tell the viewer that the scene is shifting to Edo, but these shots are often anachronistic, as the actual main keep only existed for twenty years before it burned down in the Great Meireki Fire of 1657.
As the cost of replacing it would have been enormous for the decreasingly wealthy Tokugawa shogunate, the main keep was never rebuilt, but the extensive outbuildings continued to serve as the main palace of the Tokugawa shoguns until the end of the shogunate in the Boshin War of 1868, when most of the remaining structures were burned down by rampaging Satsuma ronin.
With the establishment of the modern Japanese state and the transfer of the capital from Kyoto to Tokyo, the site of Edo Castle was renamed "Tokyo Castle," before eventually becoming the site of the current Imperial Palace, which was constructed in 1888.