Nagoya Castle is an excellent example of a flatland castle. It was completed in 1612, built at the orders of Tokugawa Ieyasu at a strategic point on the Tokaido road. It flourished under the command of the Owani clan until the Meiji Reformation eliminated the samurai class.
Unfortunately most of the castle in Nagoya was destroyed in May 1945, and was subsequently rebuilt out of ferro-concrete and other modern materials. There are still three original gates and three corner towers remaining. The interior of the main tower, called a donjon, has seven stories joined by both stairs and elevators, making it wheelchair and stroller accessible.
There are reproductions of a castle town, murals and screen paintings, armor and weapons, though very little labeling is in English. There is even a 3D movie in Japanese for visitors to learn more about the castle and its history. The grounds are small but have many plants which bloom throughout the seasons.
Nagoya Castle is open from 9 am to 4:30 pm all year, but is closed December 29-January 1. Adult admission is 500 yen and children of junior high school age or younger are free. There are many ways to reach the castle with public transportation: train, bus, and subway. From Nagoya Station, take the Marunouchi Subway to Hisaya-Odori. Transfer to the Meijo Line and get off at the Shiyakusho (M07) stop.
For more information: http://www.nagoyajo.city.nagoya.jp/13_english/index.html