The remains of a pavilion-like building where Japan's first clock, a water clock introduced from China, was placed.

It is said to have been created by Empress Saimei's son, Prince Naka no Oe (later Emperor Tenchi). A water clock on the first floor was used to measure time and a large bell on the second floor was rung to announce the time to people working in the Asuka region.

Controlling time was a privilege granted only to the most powerful person at the time (the Emperor). Many foundation stones were placed underground to prevent the pillars from sinking under the weight of the building, and the water clock demonstrates the advanced technology of manufactured copper pipes and techniques for managing water flow.

Also, since wooden calendar tablets were excavated, it is thought that not only the time of the day, but also the monthly and yearly calendars were studied and used.
The time management that began here has been passed down even today as a characteristic of the Japanese people.