Nijo Castle was one of my favorite things in Kyoto. Unfortunately, I couldn't take any photos inside the castle. The photos from the outside don't paint an appropriate image of the castle. The castle was built in 1601. It's grounds consist of 275,000 square meters, with only 8,000 of those square meters being buildings.
The best part of the castle was the nightingale floors. The floors were made to squeak like birds to protect themselves from silent intruders. The floors were so fun to walk through...there is no way anyone could walk through that castle and not be heard. The sounds are so different from what I had expected, more pleasant actually. I don't know how they designed the floors to do that, but it's pretty ingenious.