Edo Castle also had two bridges here, but the names were different. The stone bridge was a wooden bridge called 西之丸大手橋 nishi no maru ōtebashi “front bridge to the western compound” and the iron bridge was also a wooden bridge called 西之丸下乗橋 nishi no maru kejōbashi “dismount bridge to the western compound.” Nijubashi was actually the nickname of the kejōbashi (now the iron bridge), not the ōtebashi (now the stone bridge). The bridge was built in 1614 by the shōgun, Tokugawa Hidetada. The bridge had a secondary wooden support mechanism built underneath which made it a 2 level construction. Because of these two levels, it looked like there were two bridges. The nickname 二重橋 nijūbashi/futaebashi came to be used as it was quite a distinctive bridge.
When the imperial court moved into the castle in 1868 but the bridges remained. After the confiscation and destruction of the daimyō residences in Daimyō Alley and elsewhere, the old bridge and gate system was re-evaluated. The two bridges were chosen as the main entrances to Tokyo Castle (the Imperial Palace). The kejōbashi was torn down and replaced with an iron bridge in 1888. It was rebuilt again in 1964 to match the 新宮殿 Shin Kyūden the New Palace, which is the collection of shitty 60’s-looking buildings that litter the palace grounds.
Nijubashi – Tokyo’s Most Famous Bridge