I suggest you move on to the Heiseikan archeological gallery, for a complete overview of Japan through the centuries. The archeological material is displayed on the first floor, while the second floor is given over to temporary exhibitions.
For example, you can see ceramics dating to 10,000 BC, or the earliest polished stone tools in the world, dating back to the early Stone Age, 30,000 years ago. Also dedicated to Japan is the gallery featuring the treasure of the Buddhist temple Horyu-ji, the oldest wooden building in the world, mostly consisting of statues and calligraphy works.
