Nijo Castle was built in the 17th century to accommodate the Tokugawa Shoguns. Today, it's still in fantastic shape and a great place to learn about Japan in feudal times.
Your first view of Nijo Castle will be the imposing moat and bright white fortifications. There's only one open entrance to this large fortress and it's on the east side, across a large bridge. First you must purchase a ticket on the outside, by using a ticket machine. Put your money in first and then select the ticket you want (600 yen for adults and less for children).
Once inside the castle, head towards the Ninomaru Palace. Be sure to remove your shoes and put on the provided slippers. This part of the castle contains beautiful screen paintings and information about how life used to be in the castle. The first thing you may notice is that the floor squeaks like a bird! These clever nightingale floors were constructed to alert the occupants to any invaders.
After visiting the buildings within the castle, you'll get to wander through the gardens. These peaceful gardens are especially beautiful when the cherry blossoms are out or during the turning of the Fall foliage.
On the way out, you'll pass many food vendors and have the option of buying souvenirs and partaking of a snack or meal.
Nijo Castle hosts various events throughout the year. The fee is usually quite small. When I visited, in early spring, the castle was open after 6pm for nighttime viewing of the cherry blossoms. There was also live koto and taiko music being played near the exit. Be sure to ask at the entrance if anything special is taking place.