English: The Tokyo Imperial Palace is the main residence of the Emperor of Japan. It is a large park-like area located in the Chiyoda ward of Tokyo and contains several buildings including the main palace , the private residences of the imperial family, an archive, museum and administrative offices.

Two bridges led over the moats. The bridges that were once wooden and arched, were replaced with modern stone and iron cast structures in the Meiji era. The bridges were once buffered by gates on both ends, of which only the Nishinomaru-mon has survived, which is the main gate to today's Imperial Palace.

The bridge in the foreground used to be called Nishinomaru Ōte-bashi , while the one in the back was called Nishinomaru Shimojō-bashi .

After their replacement in the Meiji era, the bridge is now called Imperial Palace Main Gate Stone Bridge (kōkyo seimon ishibashi?)) and Imperial Palace Main Gate Iron Bridge (kōkyo seimon tekkyō?), respectively. The iron bridge is also known as Nijūbashi ( literally "double bridge"), because the original wooden bridge was built on top of an auxiliary bridge due to the deepness of the moat. The stone bridge is also called Meganebashi ( literally "Spectacle Bridge") because of its shape.[14] However, both bridges are often mistakenly collectively called Nijūbashi.[15]

Today both bridges are closed to the public except on January 2 and the Emperor's birthday.

en.wikipedia.org/wiki/Edo_Castle#Nij.C5.ABbashi